Computer human methods for the control and management of an airport

ABSTRACT

An Airport Control and Management Method for use by an air traffic controller which provides for a GNSS compatible computer processing environment which supports airport control and management functions in the air and on the ground. The computer system provides for automation and a computer human interface supporting air traffic controller functions. The processing environment is based upon GNSS compatible position, velocity, time information and GNSS spatially compatible databases. The computer human interface combines the data entry role of issuing clearances with automated routing, conformance monitoring and lighting control functions. The system and methods utilize precise GNSS compatible zones, the Earth Centered Earth Fixed (ECEF) WGS-84 coordinate reference frame, GNSS compatible local coordinate frames such as local and state plane grids, travel path information management processes which allow for the intelligent control of airport lighting systems. True airport independent processing is achieved when the ECEF coordinate reference frame is utilized. The system utilizes broadcast Automatic Dependent Surveillance (ADS) information from participating aircraft and vehicles Although the processing methods may be employed using other surveillance information derived from radar ot multi-lateration sources with some degradation in performance due to radar inaccuracies and inability to produce accurate 3-dimensional GNSS compatible velocity. Radio receiving equipment receives the broadcast ADS information which is then supplied to the computer system. The computer system utilizes GNSS compatible position and velocity data to control the operation of airport lights using zone incursion processing methods. The methods and processes employed provide a fundamental framework for increased airport safety, operational efficiency, energy savings and improved automation resulting in reduced controller workload.

BACKGROUND

[0001] 1. Field of the Invention

[0002] This invention is a Divisional Application of application09/598,001 filing date Jun. 20, 2000 which is Divisional Application ofapplication Ser. No. 09/032,313 filing date Feb. 27, 1998 now U.S. Pat.No. 6,195,609, a Divisional Application of Application Ser. No.08/524,081 filing date Sep. 6, 1995 now U.S. Pat. No. 5,867,804, fromDocument Disclosure # 360870 dated Sep. 2, 1994, Book “GPS Based AirportOperations, Requirements, Algorithms and Analysis, Publication Date Sep.14, 1994, Copyright Registration Nov. 10, 1994 and a continuation inpart of Ser. No. 08/117,920 filed Sep. 7, 1993 now U.S. Pat. No.5,548,515 issued Aug. 20, 1996 and application Ser. No. 08/651,837,which is a continuation in part of Ser. No 369,273 filed Jan. 5, 1995,now U.S. Pat. No. 574,648 issued Nov. 12, 1996 which is a continuationof Ser. No. 859,681, Jun. 9, 1992, abandoned, which is a continuation inpart of Ser. No. 758,852 filed as PCT/US91/07575 Sep. 10, 1991,abandoned which is a continuation-in-part of Ser. No. 593,214, Oct. 9,1990 now U.S. Pat. No. 5,200,902 issued Apr. 6, 1993.

[0003] This invention supports the control and management of surface andairborne vehicles using a computer human interface for a controller andvehicle operator supported by computer automation using Global SatelliteNavigation System data, various surveillance information, seamlessglobally applicable computer automation processing techniques andcompatible spatial and temporal databases. The GNSS compatible computerhuman interface method supports the use various surveillance systeminformation and data links for the purpose of control, management,conformance monitoring, display presentations and other airportfunctions.

[0004] 2. Description of Prior Art

[0005] Today's airport terminal operations are complex and varied fromairport to airport. Airports today are, in many cases, the limitingfactor in aviation system capacity. Each airport has a unique set ofcapacity limiting factors which may include; limited tarmac, runways,suitable approaches, navigational or/and Air Traffic Control (ATC)facilities. Furthermore, operational requirements in the terminal areainvolve all facets of aviation, communication, navigation andsurveillance. The satisfaction of these requirements withtechnological/procedural solutions should be based upon three underlyingprinciples; improved safety, improved capacity and cost effectiveness.

[0006] Today airport air traffic control procedures and general airportaviation operations are based on procedures from the 1950's. These airtraffic control procedures were initially developed to separate aircraftwhile in the air. The initial separation surveillance system was a radarsystem consisting of a rotating radar antenna. The antenna rotatedtypically about once every 4.8 seconds while transmitting a signal,another receiving antenna picks up a reflected signal from a target. Thesurveillance system then calculated a range (based on transit time) andan azimuth angle based on the physical orientation of the antenna. The2-dimensional position was then usually plotted on a display with otherdetected targets, objects and clutter. Radar today relies on fasterrotating antennas or electronically scanned antennas to provide morefrequent updates and higher resolution. To further enhance theperformance of the target returns, provide altitude information and anidentifier, a transponder is used on the aircraft. The transponder isthe key element in radar surveillance systems, since without it noidentification and no altitude information is provided to the airtraffic control system.

[0007] Surveillance data from multiple surveillance systems (radars) isthen discretely mosaiced or “tiled” into a Semi-continuous system.Controllers today separate traffic visually by the rule of “green inbetween” the target tracks. This is a highly manual method forseparation of aircraft, placing stress on the controllers and limits anytrue automation assistance for the controller.

[0008] In the high density and high precision airport environmentnumerous single function airport systems have been developed over theyears to support air traffic control and pilot needs. Precise landingnavigation is currently provided by the Instrument Landing System (ILS),while airside navigation is provided by VOR/DME, LORAN and NDB's.Airport air traffic controller surveillance is provided thorough visualmeans, airport surface detection radar (ASDE), secondary surveillanceradar, parallel runway monitoring radar and in some cases primary radar.Each of these systems is single function, local in nature and operationand provides accuracy which is a function of distance to the objectbeing tracked. Merging these navigation and surveillance systems into a4-dimensional seamless airport environment is technically difficult andexpensive. MIT Lincoln Laboratories is attempting to provide an improvedradar based Air Traffic Control environment and has received three U.S.Pat. Nos. 5,374,932, 5,519,618 and 5,570,095 reflecting those efforts.These patents relate to improvements of the current localizedsurveillance and navigation airport environment without the use of GNSScompatible seamless techniques as described herein by Pilley.

[0009] These localized systems have served the aviation system well fornearly 50 years and numerous mishaps have been prevented over thisperiod through their use. With the advent of new multi-functiontechnologies superior performance is available at a fraction of the costof today's current single function systems. The technologies of GlobalNavigation Satellite Systems, digital communication and low costcommercial computers can support seamless 4-dimensional airportoperations at smaller airports unable to justify the heavy financialinvestment in today's single function navigation and surveillancesystems.

[0010] Others are also demonstrating and developing similar systems.Haken Lans (GP&C) of Sweden is demonstrating the use of Differential GPSwith Self Organizing Time Division Multiple Access datalinkcommunications. The invention of Haken Lans is described in WorldIntellectual Property Organization document #93/01576. The invention ofFraughton describes an airborne system for collision avoidance in U.S.Pat. No. 5,153,836. The inventions of Lans and Fraughton fail to providethe seamless 4 dimensional GNSS compatible operational and processingenvironment of Pilley.

Background of the Inventor

[0011] The inventor having been involved with the FAA's AdvancedAutomation System became aware that airport program segments were notgetting the attention they deserved, nor were advanced technologiesbeing investigated. The inventor set out to demonstrate that newtechnologies could be used to support seamless airport navigation andsurveillance. The multi-year efforts of the inventors are summarized inthe book titled:

[0012] GPS BASED AIRPORT OPERATIONS, Requirements, Analysis, AlgorithmsUS copyright # TX 3 926 573, (Library of Congress # 94-69078), (ISBN0-9643568-0-5). This book provides much of the back ground for thispatent application. In addition to the book the following publicationsand professional papers have been published by the inventor in effortsof due diligence to promote this life saving technology.

Publications

[0013] Institute of Navigation, ION GPS-91, Sep. 12, 1991, TechnicalPaper, “Airport Navigation and Surveillance Using GPS and ADS”.

[0014] GPS WORLD Magazine, 10-91, Article, “GPS, Aviation and Airportsthe Integrated Solution”.

[0015] 71st Transportation Research Board, Annual Meeting, Jan. 14,1992, Technical Paper, “Applications of Satellite CNS in the TerminalArea”.

[0016] Institute of Navigation National Technical Meeting, Jan. 28,1992, Technical Paper, “Terminal Area Surveillance Using GPS”.

[0017] Institute of Navigation, ION GPS-92, Technical Paper, “CollisionPrediction and Avoidance Using Enhanced GPS”.

[0018] Institute of Navigation, 49th Annual Meeting, June 1993,Technical Paper, “Runway Incursion Avoidance Using GPS”.

[0019] Airport Surface Traffic Automation Technical Information GroupFAA & Industry Forum, Jul. 15, 1993, Presentation.

[0020] Commercial Aviation News, Jul. 19, 1993, “Airport Test to Look atCollision Avoidance”.

[0021] IEEE Vehicle Navigation and Intelligent Vehicle (VNIS),Conference, Oct. 14, 1993, Technical Paper, “Demonstration Results of

[0022] GPS for Airport Surface Control and Management”. Institute ofNavigation, ION GPS-93, Sep. 23, 1993, Technical Paper,

[0023] “GPS for Airport Surface Guidance and Traffic Management”.Avionics Magazine, 10-93, “Differential GPS Runway Navigation SystemDemonstrated”.

[0024] IEEE PLANS '94, April 1994, Technical Paper, “GPS, 3-D Maps andADS Provide A Seamless Airport Control and Management Environment”.

[0025] Institute of Navigation, ION GPS-94, Sep. 22, 1994, TechnicalPaper, DGPS for Seamless Airport Operations”.

[0026] Presentation Seattle, Wash., May 9, 1995. International CivilAviation Organization of the United Nations, Advanced Surface MovementGuidance and Control (SMGCS) meeting, Presentation and demonstration“GPS based SMGCS”.

[0027] As the list of presentations and publications shows the inventorshave been active in getting the government and the aviation community toaccept this life saving cost effective airport technology.

[0028] The United States alone currently contains some 17,000 airports,heliports and seabases. Presently only the largest of these can justifythe investment in dedicated navigation and surveillance systems whilethe vast majority of smaller airports have neither. Clearly, a newapproach is required to satisfy aviation user, airport operator, airlineand ATC needs.

[0029] It would therefore be an advance in the art to provide a costeffective Airport Control and Management System which would providenavigation, surveillance, collision prediction, zone/runway incursionand automated airport lighting control based on the Global NavigationSatellite System (GNSS) as the primary position and velocity sensor onboard participating vehicles. It would be still a further advance of theart if this system were capable of performing the navigation,surveillance, collision prediction, lighting control and zone/runwayincursion both on board the aircraft/vehicles and at a remote ATC, orother monitoring site.

[0030] With the advent of new technologies such as the GlobalPositioning System, communication and computer technology, theapplication of new technologies to the management of our airports canprovide improved efficiency, enhanced safety and lead to greaterprofitability for our aviation industry and airport operators.

[0031] On Aug. 12, 1993, Deering System Design Consultants, Inc. (DSDC)of Deering, N.H., successfully demonstrated their Airport Control &Management System (AC&M) to the Federal Aviation Administration (FAA).After many years of development efforts, the methods and processesdescribed herein were demonstrated to Mike Harrison of the FAAts RunwayIncursion Office, officials from the FAA's Satellite Program Office, theFAA New England Regional Office, the Volpe National TransportationSystem Center, the New Hampshire Department of Transportation, theOffice of U.S. Senator Judd Gregg and the Office of U.S. RepresentativeDick Swett. This was the first time such concepts were reduced to aworking demonstrable system. The inventor has taken an active stand topromote the technology in a public manner and, as such, may haveinformed others to key elements of this application. The inventor haspromoted this technology. The inventor's airports philosophy has beendescribed in general terms to the aviation industry since it was feltindustry and government awareness was necessary. The intent of thisContinuation application to identify and protect through letters ofPatent techniques, methods and improvements to the demonstrated system.

[0032] With these and other objects in view, as will be apparent tothose skilled in the art, the improved airport control and managementinvention stated herein is unique, novel and promotes the public wellbeing.

SUMMARY OF THE INVENTION

[0033] This invention most generally is a system and a method for thecontrol of surface and airborne traffic within a defined space envelope.GNSS-based, or GPS based data is used to define and create a3-dimensional map, define locations, to compute trajectories, speeds,velocities, static and dynamic regions and spaces or volumes (zones)including zones identified as forbidden zones. Databases are alsocreated, which are compatible with the GNSS data. Some of thesedatabases may contain, vehicle information such as type and shape,static zones including zones specific to vehicle type which areforbidden to the type of vehicle, notice to airmen (notams)characterized by the information or GNSS data. The GNSS data incombination with the databases is used, for example, by air trafficcontrol, to control and manage the flow of traffic approaching anddeparting the airport and the control of the flow of surface vehiclesand taxiing aircraft. All or a selected group of vehicles may have GNSSreceivers. Additionally, all or a selected group may have bi-directionaldigital data and voice communications between vehicles and also with airtraffic control. All of the data is made compatible for display on ascreen or selected screens for use and observation including screenslocated on selected vehicles and aircraft. Vehicle/aircraft data may becompatibly superimposed with the 3-dimensional map data and thecombination of data displayed or displayable may be manipulated toprovide selected viewing. The selected viewing may be in the form ofchoice of the line of observation, the viewing may be by layers basedupon the data and the objective for the use of the data.

[0034] It is, therefore, an object of this invention to provide thefollowing:

[0035] 1.) A 4-D process logic flow which provides a “seamless” airportenvironment on the ground and in the air anywhere in the world with acommon 3-D coordinate reference and time

[0036] 2.) An Airport Control and Management Method and System whichutilizes GNSS, 3-D maps, precise waypoint navigation based on the ECEFreference frame, a digital full duplex communication link and acomprehensive array of processing logic methods implemented in developedoperational software

[0037] 3.) An Airport Control and Management Method and System where avehicle based 4-D navigational computer and ATC computer utilize thesame coordinate reference and precise time standard.

[0038] 4.) A database management method compatible with 3-D waypointstorage and presentation in 3-D digital maps.

[0039] 5.) A automated method utilizing the precise 3-D airport map forthe definition and creation of airport routes and travel ways.

[0040] 6.) A 4-D process logic flow which provides precise vehiclewaypoint navigation in the air and on the ground. This process allowsfor monitoring of on or off course conditions for vehicles and aircraftoperating within the airport space envelope on board the vehicle.

[0041] 7.) A 4-D process logic flow which provides precise ATC waypointnavigation mirroring of actual vehicles in the air and on the ground atATC. This process allows for monitoring of on or off course conditionsfor vehicles and aircraft operating within the airport space envelope atthe ATC computer

[0042] 8.) A 4-D process logic flow performed on board the vehicle whichprovides for precise collision prediction based on 3-dimensional zones

[0043] 9.) A4-D process logic flow performed at the ATC computer whichprovides for precise collision prediction based on 3-dimensional zones

[0044] 10.) A collision detection management method which utilizes theapplication of false alarm reducing methods

[0045] 11.) An ATC process logic flow which detects 3-D runwayincursions. The process logic then generates message alerts and controlsairport lights

[0046] 12.) An ATC zone management method which utilizes the applicationof false alarm reducing methods

[0047] 13.) A vehicle process logic flow which detects 3-D runwayincursions. The process logic then generates message alerts and soundstones within the vehicle or aircraft

[0048] 14.) A vehicle zone management method which utilizes theapplication of false alarm reducing methods

[0049] 15.) A 4-D ATC process logic flow which manages ground and air“Clearances” with precise waypoint navigation aboard the vehicle and atthe ATC computer.

[0050] 16.) A 4-D ATC process logic flow which manages ground and air“Clearances” incorporating an integrated system of controlling airportlights.

[0051] 17.) A 4-D vehicle process logic flow which manages ground andair “Clearances” with an integrated system of waypoint navigation.

[0052] 18.) A method of management for 3-D spatial constructs calledzones

[0053] 19.) A method of management for 3-D graphical constructs calledzones

[0054] 20.) A method of management for the automated generation of azones database at any airport

[0055] 21.) A database management method for the storage of zones data.Zones database management methods are used aboard the vehicle and at ATC

[0056] 22.) A operational management method where the ATC computerprovides navigational instructions to vehicles and aircraft. Theinstructions result in a travel path with clear paths defined beingdisplayed in an airport map

[0057] 23.) A operational management method where the ATC computerprovides navigational instructions to vehicles and aircraft Theinstructions result in waypoints being entered into a 4-D navigationcomputer

[0058] 24.) A datalink message content which supports the abovemanagement methods and processes

[0059] 25.) A redundant system architecture which satisfies lifecritical airport operations

[0060] 26.) Methods for navigation within the airport environment usingmap displays, controller clearances and automation techniques in thecockpit and at ATC

[0061] 27.) An integrated airport controller automation interface whichsupports GNSS compatible processing.

[0062] 28.) A method for managing GNSS travel path information,clearances and conformance monitoring using broadcast GNSS trajectoryinformation and automatic dependent surveillance.

[0063] More specifically, the elements mentioned above form the processframework of the invention stated herein

BRIEF DESCRIPTION OF DRAWINGS

[0064] The invention, may be best understood by reference to one of itsstructural forms, as illustrated by the accompanying drawings, in which:

[0065]FIG. 1 depicts the high-level Airport Control and Managementprocessing elements and flow

[0066]FIG. 2 represents an example of a cylindrical static zone in a 3-DALP. This zone could be graphically displayed in a layer of the ALP

[0067]FIG. 3 represents an example of a static zone around aconstruction area of the airport and is used in zone incursionprocessing in the vehicles and at the ATC Processor

[0068]FIG. 4 represents an example of a dynamic zone which travels witha moving vehicle, in this case the zone represents the minimum safeclearance spacing which would be used in zone based collision detectionprocessing in the vehicles and at the ATC processor

[0069]FIG. 5 represents an example of a route zone which is defined bynavigational waypoints and is used for on/off course processing and isused in the vehicles and at the ATC Processor

[0070]FIG. 6 represents an example of a 3-D ATC zone, used to segregatetracked vehicles to particular ATC stations

[0071]FIG. 7 illustrates the construction of a 3-D runway zone

[0072]FIG. 8 shows a map display with surface waypoints and travel path

[0073]FIG. 9 shows a map display with departure waypoints and travelpath

[0074]FIG. 10 illustrates the 4-D collision detection mechanism employedin the Airport Control and Management System

[0075]FIG. 11 depicts a waypoint processing diagram showing the earthand ECEF coordinate system, expanded view of airport waypoints, furtherexpanded view of previous and next waypoint geometry with presentposition, the cross hair display presentation used in the developed GPSnavigator

[0076]FIG. 12 graphs latitude, Longitude plot of a missed approachfollowed by a touch and go with waypoints indicated about every 20seconds

[0077]FIG. 13 graphs altitude vs. time for missed approach followed bytouch and go, waypoints are indicated about every 20 seconds

[0078]FIG. 14 graphs ECEF X and Y presentation of missed approachfollowed by a touch and go with waypoints indicated about every 20seconds

[0079]FIG. 15 graphs ECEF Z versus time of missed approach followed bytouch and go, with waypoints about every 20 seconds

[0080]FIG. 16 shows a block diagram of on\off course processing

[0081]FIG. 17 shows a missed approach followed by a touch and go GPStrajectory displayed in a 3-D airport map

[0082]FIG. 18 shows an ECEF navigation screen with navigational windowinsert and 3-D digital map elements

[0083]FIG. 19 shows the area navigation display with range rings, courseand bearing radial lines, and altitude to true course indicators

[0084]FIG. 20 depicts the GPS sliding cross hair landing displayindicating too low (go up) and too far right (turn left)

[0085]FIG. 21 illustrates the GPS approach cone with digital mapelements showing current position with respect to true course line

[0086]FIG. 22 depicts the demonstration system airport communicationsdiagram showing processor, DGPS base station, radio elements and messageflows

[0087]FIG. 23 depicts the demonstration system AC&M hardware blockdiagram showing various elements of the system

[0088]FIG. 24 depicts the demonstration system aircraft hardware blockdiagram

[0089]FIG. 25 depicts the demonstration system vehicle #1 hardware blockdiagram

[0090]FIG. 26 depicts the demonstration system vehicle #2 hardware blockdiagram

[0091]FIG. 27 shows the navigator display compass rose area navigatorand cross hair sliding precision approach display in combination withwaypoint information, position, velocity, range to the waypoint, crosstrack error, speed, heading and distance to true course

[0092]FIG. 28 depicts the airport system single controller station, nonredundant design

[0093]FIG. 29 depicts the airport system redundant single controllerstation

[0094]FIG. 30 depicts the airport system redundant dual controllerstation

[0095]FIG. 31 depicts the map temporal differential correction systemdiagram

[0096]FIG. 32 depicts the differential GPS system diagram

[0097]FIG. 33 depicts the closed loop differential GPS system diagram

[0098]FIG. 34 depicts the computer human interrface using a touch screen

DESCRIPTION OF PREFERRED EMBODIMENT

[0099] AC&M PROCESSING OVERVIEW

[0100] The primary Airport Control and Management (AC&M) functions ofthe invention utilize a Cartesian ECEF X, Y, Z coordinate framecompatible with GNSS. FIG. 1 provides additional detail for theoperational elements of the AC&M processing. The GNSS signals broadcastby the vehicles 8 are processed by the Real Time Communication Handler 3and sent to AC&M Operational Control 1. The Operational Control 1 usesthe GNSS data to perform the following processing functions 5: positionprojections, coordinate conversions, zone detection, collisionprediction, runway incursion detection, layer filter, alarm control, andlighting control. If waypoints have been issued to the vehicle 8,mirrored waypoint navigation is also performed by the AC&M processing.The Operational Control 1 interfaces directly to the Graphical Control2. Graphics messages, including GNSS data and coded informationpertaining to zone incursions, possible collision conditions, or offcourse conditions detected by the AC:&M Processing, are passed to theGraphical Control 2. The Graphical Control 2 interprets this data andupdates the display presentation accordingly.

[0101] The Operational Control 1 function also receives inputs from theController/Operator Interface 6. The controller/Operator Interface usesthe data received by Controller/Operator Inputs 7 to compose ATCcommands which are sent to the Operational Control 1 function forprocessing. Commands affecting the presentation on the computer displayscreen are sent by the Operational Control 1 function to the GraphicalControl 2. ATC commands composed by the Controller/Operator Interface 6processing that do not require further AC&M processing are forwardeddirectly to the Graphical Control 2 to update the display screen. Boththe Operational Control 1 function and Graphical Control 2 processinghave access to the Monumentation, Aircraft/Vehicle, Static Zones,Waypoints, Airport Map, ATIS Interface and Airport Status and other lowlevel data bases 9 to process and manipulate the presentation of map andvehicle data on a computer display screen.

[0102] More specifically, each vehicle 8 supports the capability totransmit a minimum of an identifier, the GNSS referenced position of oneor more antennas, velocity, optional acceleration and time reports.Since this data is broadcast, it is accessible to the airport controltower, other aircraft and vehicles in the local area, and variousairline monitoring or emergency command centers which may performsimilar processing functions. ATC commands, processed by theController/Operator Interface 6 and Operational Control 1 function arepassed to the Real Time Communication Handler 3 for transmission to theaircraft/vehicle(s) 8. Upon receipt of ATC messages, the vehicle(s) 8return an acknowledgment message which is received by the Real Timecommunication Handler 3 and passed to the Operational Control 1function. Differential GNSS corrections are generated by theDifferential GPS Processor 4 and passed to the Real Time CommunicationHandler 3 for broadcast to the vehicles. The Real Time CommunicationHandler 8 performs the following functions at a minimum:

[0103] a. Initialize ATC computer communication lines

[0104] b. Initialize radio equipment

[0105] c. Establish communication links

[0106] d. Receive vehicle identifier, positions, velocity, time andother information

[0107] e. Receive information from ATC Processor to transmit tovehicle(s)

[0108] f. Receive ATC acknowledgment messages from vehicle(s)

[0109] g. Transmit information to all vehicles or to selected vehiclesby controlling frequency and/or identifier tags

[0110] h. Monitor errors or new information being transmitted

[0111] i. Receive and broadcast differential correction data

[0112] The AC&M techniques and methods described herein provide for GNSScompatible 4-Dimensional Airport Control and Management.

[0113] THE 3-D DIGITAL AIRPORT LAYOUT PLAN

[0114] The combination of ECEF navigation combined with NAD 83 (Lat,Lon, MSL and State Plane) and WGS 84 (X,Y,Z) based 3-D airport featuresare necessary in constructing an airport layout plan (ALP). The AirportControl and Management System (AC&M) requires that navigation andAutomatic dependent Surveillance (ADS) information used in collisiondetection processing share the same coordinate frame. The processingmethods described herein, require very accurate and properly monumentedairport layout plans. Physical features surrounding the airport may besurveyed in a local coordinate frame and, as such, require accuratetransformation into the airport map/processing coordinate frame. Forthese reasons, the use of multi-monumented coordinate references ismandatory for such map construction and survey. Clearly, highly accurate3-D maps are required when using precise GNSS based navigation,collision avoidance and overall Airport Control and Management for lifecritical airport applications.

[0115] The 3-D ALP database and display presentation support the conceptof zones. The display of zone information is managed using the Map LayerFilter. Zones are two and three dimensional shapes which are used toprovide spatial cueing for a number of design constructs. Static zonesmay be defined around obstacles which may pose a hazard to navigationsuch as transmission towers, tall buildings, and terrain features. Zonesmay also be keyed to the airport's NOTAMS, identifying areas of theairport which have restricted usage. Dynamic zones are capable ofmovement. For example, a dynamic zone may be constructed around movingvehicles or hazardous weather areas. A route zone is a 3-D zone formedalong a travel path such as a glide slope. Zone processing techniquesare also applied to the management of travel clearances and for thedetection of runway incursions. Zones may also be associated with eachaircraft or surface vehicle to provide collision prediction information.

[0116] OPERATIONAL PROJECTIONS

[0117] AC&M projection processing utilizes received GNSS ADS messagesfrom a datalink. The complete received message is then checked forerrors using CRC error detection techniques or a error correcting code.The message contains the following information, or a subset thereof, butnot limited to: PVT ADS DATA ID #  8 Characters VEHICLE TYPE  4Characters CURRENT POSITION: X=ECEF X Position (M) 10 Characters Y=ECEFY Position (M) 10 Characters Z=ECEF Z Position (M) 10 Characters X2=ECEFX2 Position (M)  2 Characters * Y2=ECEF Y2 Position (M)  2 Characters *Z2=ECEF Z2 Position (M)  2 Characters * X3=ECEF X3 Position (M)  2Characters * Y3=ECEF Y3 Position (M)  2 Characters * Z3=ECEF Z3 Position(M)  2 Characters * VX=ECEF X Velocity (M/S)  4 Characters VY=ECEF YVelocity (M/S)  4 Characters VZ=ECEF Z Velocity (M/S)  4 CharactersAX=ECEF X Acceleration (M/S2)  2 Characters # AY=ECEF Y Acceleration(M/S2)  2 Characters # AZ=ECEF Z Acceleration (M/S2)  2 Characters #TIME  8 Characters TOTAL CHARACTERS/MESSAGE: 80 Characters

[0118] A database is constructed using the ADS message reports. The AC&Mprocessing converts the position and velocity information to theappropriate coordinate frame (if necessary, speed in knots and a truenorth heading). Simple first and second order time projections basedupon position, velocity and acceleration computations are used. Theability to smooth and average the velocity information is also possibleusing time weighted averages.

[0119] ECEF POSITION PROJECTION TECHNIQUE

PROJECTED X=X+(VX)(t)+(AX)(t ²)/2

PROJECTED Y=Y+(VY)(t)+(AY)(t ²)/2

PROJECTED Z=Z+(VZ)(t)+(AZ)(t ²)/2

[0120] This set of simple projection relationships is used in thecollision prediction and zone incursion processing methods.

[0121] ZONE DATABASE

[0122] Zone areas may be defined in the initial map data baseconstruction or may be added to the map database using a 2-D or 3-D dataentry capability. The data entry device may be used to construct a zoneusing a digital map in the following manner:

[0123] Using the displayed map, the data entry device is used to enterthe coordinates of a shape around the area to be designated as a zone.(An example may be a construction area closed to aircraft traffic listedin the current NOTAMS.)

[0124] The corners of the polygon are saved along with a zone type codeafter the last corner is entered. Circles and spheres are noted by thecenter point and a radius, cylinders are noted as a circle andadditional height qualifying information. Other shapes are defined andentered in a similar fashion.

[0125] The zone is stored as a list of X, Y, Z coordinates. Linesconnecting the points form a geometric shape corresponding to thephysical zone in the selected color, line type and style in the properlayer of the base map.

[0126] Zone information may then be used by collision detection andboundary detection software contained in the AC&M system. Thisprocessing software is explained later in this specification.

[0127]FIG. 2 depicts a 3-D cylindrical static zone around a hypotheticalutility pole. This zone 10 is added into the airport map 11, while thespecific coordinates (center point of base 12, radius of circular base13, and the height 14) are saved to the zone file list in a convenientcoordinate frame. Below is an example of a zone which is stored in thezone database. IDENTIFIER PARAMETER Utility pole Type of Zone Center ofbase X, Y, Z Radius of base R Height of the cylinder H

[0128] The 3-D digital map 11 is then updated using a series of graphicinstructions to draw the zone 10 into the map with specific graphiccharacteristics such as line type, line color, area fill and othercharacteristics. A database of zone information containing zones insurface coordinates such as X & Y state plane coordinates and mean sealevel, ECEF referenced X, Y, Z and others are accessible to the AC&MProcessing. The database may consist of, but is not limited to thefollowing type of zones.

[0129] OBJECT OF THE ZONE

[0130] ___________________

[0131] TRANSMISSION TOWERS

[0132] AIRPORT CONSTRUCTION AREAS

[0133] CLOSED AREAS OF AIRPORT

[0134] MOUNTAINS

[0135] TALL BUILDINGS

[0136] AREAS OFF TAXIWAY AND RUNWAY

[0137] RESTRICTED AIRSPACE

[0138] INVISIBLE BOUNDARIES BETWEEN AIR TRAFFIC CONTROLLER AREAS

[0139] APPROACH ENVELOPE

[0140] DEPARTURE ENVELOPE

[0141] AREAS SURROUNDING THE AIRPORT

[0142] MOVING ZONES AROUND AIRCRAFT/VEHICLES

[0143] ZONE PROCESSING

[0144] The zone information is retrieved from a zone database. As theAC&M Processor receives current ADS reports, information on eachposition report is checked for zone incursion. Further processingutilizes velocity and acceleration information to determine projectedposition and potential collision hazards. If a current position orprojected position enters a zone area or presents a collision hazard analert is generated.

[0145] A zone is any shape which forms a 2-D or 3-D figure such as butnot limited to a convex polygon (2-D or 3-D), or a circular (2-D),spherical (3-D), cylindrical (3-D) or conical shape represented as amathematical formula or as a series of coordinate points. Zones arestored in numerous ways based upon the type of zone. The coordinatesystem of the map and the units of measure greatly affect the manner inwhich zones are constructed, stored and processed.

[0146] The invention described herein utilizes four primary types of 2-Dand 3-D zones in the Airport Control and Management System.

[0147] FOUR PRIMARY ZONE TYPES

[0148] The first type zone is a static zone as shown in FIG. 3. Staticzones represent static non-moving objects, such as radio towers,construction areas, or forbidden areas off limits to particularvehicles. The zone 15 shown in the FIG. 3 represents a closed area ofthe airport which is under construction. The zone 15 is a 3-D zone witha height of 100 Meters 16, since it is desired not to have aircraftflying low over the construction site, but high altitude passes over thezone are permitted. An example of a permitted flyover path 17 and aforbidden fly through path 18 are shown in the figure. The fly throughwill produce a zone incursion, while the flyover will not.

[0149] A second zone type is shown in FIG. 4 and represents a dynamiczone 19 which moves with a moving vehicle or aircraft. Dynamic zones maybe sized and shaped for rough check purposes or may be used to describethe minimum safe clearance distance. The dynamic zone is capable ofchanging size and shape as a function of velocity and or phase of flightand characterized by vehicle or aircraft type.

[0150] The third type zone is shown in FIG. 5 and is a route zone 20.Route zones are described though the use of travel waypoints 21 and 22.The waypoints 21 and 22 define the center line of a travel path, thezone has a specified allowable travel radius X1, Y1 at Waypoint 1 21 andX2, Y2 at Waypoint 2 22 for the Determination of on or off courseprocessing. For simplicity X1 may equal X2 and Y1 may equal Y2. Oncourse 23 operations result in travel which is within the zone, whileoff course 24 operations result in travel which is outside the zone andresult in an off course warning.

[0151] The fourth type zone(s) shown in FIG. 6 is a 3-D zone which isdynamic and used to sort ATC traffic by. This type zone is used tosegregate information to various types of controller/operator positions,i.e. ground control, clearance delivery, Crash Fire and Rescue andothers. Travel within a particular zone automatically defines which ATCposition or station the traffic is managed by. For example travel withinzone 1 25 is directed to ATC ground station, while travel within zone 226 is directed to ATC Clearance Delivery position. The ATC zone conceptallows for automatic handoff from one controllers position to the otheras well as providing overall database the management automation.

[0152] The construct of zones is very important to the overall operationof the described invention herein. Further examples of zone processingmethods and zone definition is provided below.

EXAMPLE 1

[0153] A cylindrical zone on the airport surface constructed using thestate plane coordinate system would be represented as the following:Center point of circle CXsp value, CYsp value Elevation (MSL) Elev =constant, or may be a range Circle radius CR value

[0154] The detection of a zone incursion (meaning that the position iswithin the 2-D circle) is described below. Convert position to StatePlane coordinates Current or projected position Xsp, Ysp Subtract circlecenter Xsp − CXsp = DXsp from current position Ysp − CYsp = DYspDetermine distance from DXsp² + Dysp² = Rsp² circle center Test ifposition is in Rsp <= CR circle If true continue  If not true exit notin zone Test if position is Min Elev <= Elev <= Max Elev within altituderange (a cylindrical zone)

[0155] If the above conditions are met, the position is in the 3-Dcylindrical zone. It can be seen that the basic methods used here areapplicable to other grid or coordinate systems based on lineardistances.

EXAMPLE 2

[0156] A cylindrical zone on the airport surface (normal with theairport surface) constructed using the Earth Centered Earth Fixedcoordinate system is stored using three axis (X, Y, Z). Convert currentposition to ECEF X, Y, Z Center point of circle CX value, CY value, CZvalue Circle radius CR value Determine distance from (X − CX) = DXcurrent or projected position (Y − CY) = DY to center of circle (Z − CZ)= DZ Determine radial distance DX² + DY² + DZ² = R² to circle centerpoint from current position Test position to see if it R <= CR is insphere of radius R If true continue  If not true exit not in zoneDetermine the vector between VC = CXE + CYE + CZE the center of thecircle and the center of mass of the earth Calculate its magnitude VC² =CXE² + CYE² + CZE² Determine the vector between the V = VX + VY + VZcenter of mass of the earth and the current or projected positionCalculate its magnitude V² = VX² + VY² + VZ² Determine the differencebetween V − VC = 0 the two vectors, if result = 0 then in the 2-D zone,if the result is <0 then position is below, if >0 then position is abovethe zone

[0157] To check for incursion into an ECEF cylindrical zone, thefollowing is tested for. Test if position is Min VC <= V <= Max VCwithin Vector range (a cylindrical zone) Where Min VC represents thebottom of the cylinder Max VC represents the top of the cylinder

[0158] The final two tests use an approximation which greatly simplifiesthe processing overhead associated with zone incursion detection. Theassumption assumes that over the surface area of an airport, the vectorbetween the center of mass of the earth circular zone center and thevector from the current position to the center of the circle arecoincident. That is, the angle between the two vectors is negligible.

[0159] The second assumption based on the first approximation is that,rather than perform complex coordinate reference transformations forzone shapes not parallel with the earth's surface, projections normal tothe surface of the earth will be used. Zones which are not parallel withthe earth's surface are handled in a manner similar to that applied toon or off course waypoint processing using rotation about a point orcenter line.

EXAMPLE #3

[0160] A zone which is shaped like a polygon is initially defined as aseries of points. The points may be entered using a data entry deviceand a software program with respect to the digital map or they may bepart of the base digital map. The points are then ordered in a mannerwhich facilitates processing of polygon zone incursion. The followingexamples indicate how a (4 sided) polygon is stored and how an airportsurface zone incursion is performed using both the state planecoordinates and Earth Centered Earth Fixed X, Y, Z coordinates. ConvertPosition to SP Xsp, Ysp, State Plane Zone X1sp, Y1sp; X2sp, Y2sp;Vertices X3sp, Y3sp; X4sp, Y4sp Order in a clockwise direction Height of3-D zone min Elev max Elev Determine min & max Xspmax, Xspmin, Yspmax,Yspmin values for X & Y Perform rough check Is Xspmin <= Xsp <= Xspmaxof current position Is Yspmin <= Ysp <= Yspmax or projected position Ifboth true then continue with zone checking  If not true exit, not inzone Calculate the slope (Y2sp − Y1sp)/(X2sp − X1sp)= M of the linebetween points 1 & 2 Calculate the slope of M⁻¹= −Mnor the line from thepresent position normal to the line between points 1 & 2 Determine theequation Y1sp − M * X1sp = L between points 1 & 2 Determine the equationYsp − Mnor * Xsp = LN for the line normal to the line between points 1 &2 and position Determine the intersection intXsp = (LN − L)/(M−Mnor) ofboth lines intYsp = Mnor * intXsp + (Ysp − Mnor * Xsp) Determine theoffset from Xsp − intXsp = DXsp position to intersect Ysp − intYsp =DYsp point on the line between points 1 & 2 Perform check to see whichCheck the sign of DXsp side of the line the position is on Check thesign of Dysp (note sign change as function of quadrant & direction inwhich points are entered in) If the point is on the proper Meaning thesigns are side continue and check o.k. the next line between points 2 &3 and perform the same analysis If the line is on the wrong side of theline, then not in the zone hence exit If point is on the proper side ofall (4) lines of polygon then in 2-D zone Note: If the zone vertices areentered in a counter clockwise direction the sign of DXsp and DYsp areswapped. Test if position is Min Elev <= Elev <= Max Elev withinaltitude range (a 3-D polygon zone)

EXAMPLE #4

[0161] A further example is provided in the definition of a 3-D runwayzone using ECEF X,Y,Z. A list of runway comers is constructed using the3-D map and a data entry device and an automated software tool. Therunway zone is shown in FIG. 7.

[0162] The horizontal outline the runway 27 by selecting the four comersC1,C2,C3,C4 in a clockwise direction 28, starting anywhere on the closedconvex polygon formed by the runway 27

[0163] Define the thickness of the zone (height above the runway) 29

[0164] The 4 comer 3-D coordinates and min and max altitudes areobtained through the use of a program using the ALP, then conversion areperformed if necessary to convert from ALP coordinates to ECEF X, Y, Zvalues. C1 = X1, Y1, Z1 C2 = X2, Y2, Z2 C3 = X3, Y3, Z3 C4 = X4, Y4, Z4MINALT = SQRT(XMIN² + YMIN² + ZMIN²) MAXALT = SQRT(XMAX² + YMAX² +ZMAX²) HEIGHT = MAXALT − MINALT

[0165] Define the (4) planes formed by the vectors originating at thecenter of mass of the earth and terminating at the respective fourrunway corners. Represent the 4 planes by the vector cross product asindicated below: XP1 = C1 × C2 XP2 = C2 × C3 XP3 = C3 × C4 XP4 = C4 × C1

[0166] Store the vector cross products in the polygon zones database,where the number of stored vector cross products equals the number ofsides of the convex polygon

[0167] Determine if the present position or projected position is withinthe zone (PP=position to be checked)

PP=PX1, PY1, PZ1

[0168] Determine the scalar Dot product between the current position andthe previously calculated Cross Products DP1 = PP * XP1 DP2 = PP * XP2DP3 = PP * XP3 DP4 = PP * XP4

[0169] If the products are negative then PP is within the volume definedby intersection planes, if it is positive then outside the volumedefined by the intersecting planes,

[0170] Note: the signs reverse if one proceeds around the zone in acounter clockwise direction during the definition process

[0171] Determine if PP is within the height confines of the zoneDetermine the magnitude of the PP vector, for an origin at center ofmass of the earth.

PPM=SQRT[(PX 1)²+(PY 1)²+(PZ 1)²]

[0172] Compare PPM=(PP magnitude) to minimum altitude of zone andmaximum altitude of zone

MINALT<=PPM<=MAXALT

[0173] If the above relationship is true then in the zone.

[0174] If false then outside of the zone

[0175] An alternate method of determining if the present position PP iswithin a zone which is not normal to the earth's surface is determinedusing a method similar to that above, except that all N sides of thezone are represented as normal cross products, the corresponding Dotproducts are calculated and their total products inspected for sign.Based upon the sign of the product PP is either out of or inside of thezone.

[0176] An example of actual Zone and Runway Incursion software code iscontained shown below. The actual code includes interfaces to lightcontrol, clearance status, tones and other ATC functions.

[0177] Since the extension to polygons of N sides based upon theprevious concepts are easily understood, the derivation has been omittedfor the sake of brevity.

[0178] In summary two mathematical methods are identified for detectingzone incursions into convex polygons, one based on the equation andslope of the lines, the other is based on vector cross and dot productoperators.

[0179] The concept of zones, regardless as to whether they arereferenced to surface coordinates, local grid systems or ECEFcoordinates, provide a powerful analytical method for use in the AirportControl and Management System.

[0180] ZONE BASED CLEARANCES

[0181] The airport control and management system manages overall taxi,departure and arrival clearances in a unique and novel manner throughthe use of zone processing. A departure ground taxi clearance is issuedto the selected vehicle. The waypoints and travel path are drawn intothe map aboard the selected vehicle. The vehicle(s) then use thepresented taxi information to proceed to the final waypoint. AC&Mprocessing uses this clearance information to mask runway zoneincursions along the travel path. Since runway incursions are masked foronly the selected vehicle and for zones traversed no runway incursionalert actions or warning lights are produced when following the propercourse. Should the position represent movement outside of theextablished corridor, an alert is issued signifing an off coursecondition exist for that vehicle. Upon the vehicle exit from aparticular “cleared” zone, the mask is reset for that zone. Once thelast waypoint is reached the clearance is removed and the zone mask isreset. The description below details how such clearances are managed.

[0182] SURFACE DEPARTURE CLEARANCE MANAGEMENT METHOD

[0183] 1. The operator or controller wishes to issue a surface departureclearance to a specific vehicle.

[0184] 2. Through the use of a data entry device such as a touch screenor keyboard or mouse, issue waypoints command is selected for surfacedeparture waypoints

[0185] 3. The operator is asked to select a specific vehicle from a listof available aircraft and vehicles

[0186] 4. The vehicle data window then displays a scrollable list ofavailable vehicles contained in a database which are capable ofperforming operations of departure clearance

[0187] 5. The operator then selects the specific vehicle using a dataentry device such as a touch screen or other data entry device

[0188] 6. A list is then displayed in a scrollable graphical window ofavailable departure travel paths for the selected vehicle

[0189] 7. The operator then selects from this list using a data entrydevice such as a touch screen or other data entry device

[0190] 8. Upon selection of a particular departure path the waypointsand travel path are drawn into a 3-D ALP. The purpose of presentation isto show the controller or operator the actual path selected

[0191] 9. The controller or operator is then asked to confirm theselected path. Is the selected path correct? Using a data entry devicesuch as a touch screen or other data entry device a selection is made.

[0192] 10. If the selected path was not correct, then the command isterminated and no further action is taken

[0193] 11. If the selection was correct the following steps are takenautomatically.

[0194] a. AC&M processing sends to the selected vehicle using a radioduplex datalink, the clearance, 4-D waypoint and travel path information

[0195] b. The selected vehicle upon receipt of the ATC command replieswith an acknowledgment. The acknowledgment is sent over the full duplexradio datalink to the AC&M processing

[0196] c. Should the AC&M processing not receive the acknowledgment in aspecified amount of time from the selected vehicle, a re-transmissionoccurs up to a maximum of N re-transmissions

[0197] d. The vehicle upon receiving the ATC command then “loads” the4-D navigator with the 4-D waypoint information. A map display containedin the vehicle then draws into the 3-D ALP the departure travel path asshown in FIG. 8. This figure shows travel path as 30 in the digital ALP31 while actual waypoints are shown as (14) spheres 32.

[0198] DEPARTURE CLEARANCE MANAGEMENT METHOD

[0199] 1. The operator or controller wishes to issue a departureclearance to a specific aircraft

[0200] 2. Through the use of a data entry device such as a touch screenor keyboard or mouse, issue waypoints command is selected for departurewaypoints

[0201] 3. The operator is asked to select a specific vehicle from a listof available aircraft

[0202] 4. The vehicle data window then displays a scrollable list ofavailable aircraft contained in a database which are capable ofperforming operations of departure clearance

[0203] 5. The operator then selects the specific vehicle using a dataentry device such as a touch screen or other data entry device

[0204] 6. A list is then displayed in a scrollable graphical window ofavailable departure travel paths for the selected vehicle

[0205] 7. The operator then selects from this list using a data entrydevice such as a touch screen or other data entry device

[0206] 8. Upon selection of a particular departure path the waypointsand travel path are drawn into a 3-D ALP. The purpose of presentation isto show the controller or operator the actual path selected

[0207] 9. The controller or operator is then asked to confirm theselected path. Is the selected path correct? Using a data entry devicesuch as a touch screen or other data entry device a selection is made.

[0208] 10. If the selected path was not correct, then the command isterminated and no further action is taken

[0209] 11. If the selection was correct the following steps are takenautomatically.

[0210] a. AC&M processing sends to the selected vehicle using a radioduplex datalink, the clearance, 4-D waypoint and travel path information

[0211] b. The selected vehicle upon receipt of the ATC command replieswith an acknowledgment. The acknowledgment is sent over the full duplexradio datalink to the AC&M processing

[0212] c. Should the AC&M processing not receive the acknowledgment in aspecified amount of time from the selected vehicle, a re-transmissionoccurs up to a maximum of N re-transmissions

[0213] d. The vehicle upon receiving the ATC command then “loads” the4-D navigator with the 4-D waypoint information. A map display containedin the vehicle then draws into the 3-D ALP the departure travel path asshown in FIG. 9. This figure shows travel path as 34 in the digital ALP35 while actual waypoints are shown as (5) spheres 36.

[0214] 12. Upon AC&M receiving the acknowledgment, the following isperformed:

[0215] a. the zone mask is updated indicating that the selected vehiclehas a clearance to occupy runway(s) and taxiway(s) along the travelpath. This mask suppresses zone runway incursion logic for this vehicle.

[0216] b. the zone based lighting control processing then activates theappropriate set of airport lights for the issued clearance in this caseTake Off Lights

[0217] 13. The vehicle now has active navigation information and maystart to move, sending out ADS message broadcasts over the datalink toother vehicles and the AC&M system

[0218] 14. The selected vehicle ADS messages are received at the AC&Msystem and at other vehicles.

[0219] 15. AC&M processing using information contained in the ADSmessage performs mirrored navigational processing, as outlined in alatter section.

[0220] 16. Zone incursion checking is performed for every received ADSmessage using position projection techniques for zones contained in thezones database

[0221] 17. Should a zone incursion be detected, the zone mask is used todetermine if the incurred zone is one which the vehicle is allowed to bein. If the zone is not in the zone mask then a warning is issued. Shouldthe zone be that of a Runway, a Runway Incursion Alert is Issued and theappropriate airport lights are activated.

[0222] 18. The ADS position is used to determine when the vehicle leavesa zone. When the vehicle leaves the zone, the clearance mask is updatedindicated travel though a particular zone is complete. When this occursthe following steps are initiated by the AC&M:

[0223] a. the zones mask is updated

[0224] b. airport light status is updated

[0225] If the exited zone was a Runway, operations may now occur on theexited runway

[0226] 19. The vehicle continues to travel towards the final waypoint

[0227] 20. At the final waypoint the navigator and the map display arepurged of active waypoint information, meaning the vehicle is where itis expected to be. New waypoints may be issued at any time with awaypoints command function.

[0228] AC&M zones based clearance function as presented here provides aunique and automated method for the controlling and managing airportsurface and air clearances.

[0229] COLLISION DETECTION

[0230] Collision detection is performed through the zones managementprocess. The basic steps for collision detection and avoidance are shownbelow in a general form. FIG. 10 shows graphically what the followingtext describes.

[0231] 1. Vehicle Position, Velocity and Time (PVT) information arereceived for all tracked vehicles. The following processing is performedfor each and every ADS vehicle report

[0232] 2. PVT information is converted to the appropriate coordinatesystem if necessary and stored in the database

[0233] 3. A rough check zone 38 and 39 is established based on thecurrent velocity for each vehicle in the database

[0234] 4. Every vehicle's rough check radius is compared with everyother vehicle in the database. This is done simply by subtracting thecurrent position of vehicle V from the position of vehicle V+1 in thedatabase to determine the separation distance between each vehicle andevery other vehicle in the database. This is performed in the ECEFcoordinate frame.

[0235] 5. For each pair of vehicles in the database that are within thesum of the two respective rough check radii values; continue furtherchecking since a possible collision condition exists, if not within thesum of the rough check radii do no further processing until the next ADSmessage is received

[0236] 6. For each set of vehicles which have intersecting rough checkradii project the position ahead by an increment of Time (t) using thereceived vehicle velocity and optionally acceleration information.Projected positions at time=T1 are shown by two circles 40 and 41 theminimum safe clearance separation for the fuel truck R1 and aircraft R2respectively.

[0237] 7. Determine the new separation distance between all vehicleswhich initially required further checking. Compare this distance to thesum of minimum safe clearance distances R1 and R2 for those vehicles atthe new incremented time. The minimum safe clearance distances R1 and R2are contained in a database and is a function of vehicle velocity andtype. Should the separation distance 42 between them be less than thesum of the minimal safe clearance distances R1+R2, then generate alertwarning condition. Record the collision time values for each set ofvehicles checked. If no minimum safe clearance distance is violated thencontinue checking the next set of vehicles in a similar fashion. Whenall vehicles pairs are checked then return to the start of the vehicledatabase.

[0238] 8. Increment the projection time value (T+t) seconds and repeatstep 7 if separation was greater than the sum of the minimal safeseparation distance R1+R2. Continue to increment the time value to amaximum preset value, until the maximum projection time is reached, thenprocess next pair of vehicles in a similar fashion, until the lastvehicle is reached at that time start the process over. If minimum safeclearance (R1+R2) was violated compare the time of intersection to theprevious time of intersection. If the previous intersection time is lessthan the new intersection time the vehicles are moving apart, nocollision warning generated. In the event that the vehicles are movingtogether, meaning the intersection times are getting smaller, determineif a course change is expected based upon the current waypoints issued,and if the course change will eliminate the

[0239] collision condition. If a course change is not expected or if thecourse change will not alleviate the collision situation then generatealert. If the projection time T is less than the maximum projection timefor warning alerts, generate a warning. If the projection time T isgreater than the maximum projection time for a warning alert and lessthan the maximum projection time for a watch alert, generate a watchalert. If the projection time T is greater than the maximum projectiontime for a watch alert generate no watch alert.

[0240] 9. The warning condition generates a message on the ALERT displayidentifying which vehicles are in a collision warning state. It alsoelevates the layer identifier code for those vehicle(s) to an alwaysdisplayed (non-maskable) warning layer in which all potentiallycolliding vehicles are displayed in RED.

[0241] 10. The watch condition generates a message on the ALERT displayidentifying which vehicles are in a collision watch state. It alsoelevates the layer identifier code for that vehicle(s) to an Alwaysdisplayed (non-maskable) watch layer in which all potentially collidingvehicles are displayed in YELLOW.

[0242] 11. The process continually runs with each new ADS messagereport.

[0243] COLLISION PROCESSING SOFTWARE EXAMPLE

[0244] The sample code below performs the above collision processing,without the routine which checks for course changes, to reduce falsealarms.

[0245] ON OR OFF COURSE PROCESSING

[0246] The AC&M processing performs mirrored navigational processingusing the same coordinate references and waypoints as those aboard thevehicles. In this manner the ATC system can quickly detect off courseconditions anywhere in the 3-D airport space envelope and effectivelyperform zone incursion processing aboard the vehicles and at the AC&M.

[0247] The AC&M processing software converts the position and velocityinformation to the appropriate coordinate frame (zone & map compatible)using techniques described previously. Waypoints based upon the precise3-dimensional map are used for surface and air navigation in the airportspace envelope. The capability is provided to store waypoints in avariety of coordinate systems, such as conventional Latitude, Longitude,Mean Sea Level, State Plane Coordinates, ECEF X, Y, Z and others. Thenavigational Waypoint and on course—off course determinations arepreferred to be performed in an ECEF X, Y, Z coordinate frame, but thisis not mandatory.

[0248] The following mathematical example is provided to show howwaypoints and trajectories are processed in Latitude, Longitude, MeanSea Level and in ECEF X, Y, Z. An actual GNSS flight trajectory is usedfor this mathematical analysis. The flight trajectory has beenpreviously converted to an ECEF X, Y, Z format as have the waypointsusing the previously described techniques. FIGS. 11,12,13,14,15 are usedin conjunction with the following description.

[0249]FIG. 11 depicts the ECEF waypoint processing used in the AC&M. TheECEF coordinate system 43 is shown as X,Y,Z, the origin of thecoordinate system is shown as 0,0,0. The coordinate system rotates 44with the earth on its polar axis. The airport 45 is shown as a squarepatch. An enlarged side view of the airport 46 is shown with (4)waypoints 47. A further enlargement shows the Present Position 48 (PP),the Next Waypoint 49 (NWP) the Previous Waypoint (PWP) 50. The TrueCourse Line 58 is between the Next Waypoint 49 and Previous Waypoint 50.The vector from the Present Position 48 to the Next Waypoint 49 isvector TNWP 51. The Velocity Vector 52 and the Time Projected Positionis shown as a solid black box 53. The Projected Position 53 is used inzone incursion processing. The 3-D distance to the true coarse isrepresented by the Cross Track Vector 54 XTRK. The vector normal to theearth surface at the present position and originating at the center ofmass of the earth is shown as 55. This vector is assumed to be in thesame direction of the vertical axis 56. The lateral axis 57 isperpendicular to the vertical axis and perpendicular to the true courseline 58 between the Next Waypoint 49 and the Previous Waypoint 50. TheNavigational Display 59 shows the Present Position 48 with respect tothe True Course Line 58.

[0250] The following equations describe the processing performed in theAC&M while FIGS. 12, 13, 14, and 15 represent plots of the actualtrajectory information. Variable Definition Ω = the number of degreesper radian 57.295779513 α = semi major axis, equatorial radius 6378137meters e = earth's eccentricity 0.0818182 TALT = ellipsoidal altitude oftrajectory position (meters) WALT = ellipsoidal altitude of the waypointpositions (meters) ρ = earth's radius of curvature at the position orwaypoint r = 2-d equatorial radius (meters) R = first estimate of theradius of curvature (meters) sφ = the ratio of ECEF Z value divided by R(meters) RC = radius of curvature at the present position (meters) h =altitude with respect to the reference ellipsoid (meters) λ = longitudeof position in radians φ = latitude of position in radiams ENU = East,North, Up coordinate reference XYZ = East, North, Up vector distance(meters) to waypoint VELENU = East, North, Up velocity in (meters/sec)DISTENU = East, North, Up scalar distance to waypoint VELEMUMAG = East,North, Up Velocity magnitude (scalar) meters/sec NBEAR = True NorthBearing

[0251] T=Time in seconds

[0252] p_(wT)=Earth's radius of curvature at the waypoint

[0253] Waypoint indexes through a list of waypoints

[0254] Waypoints are indexed as a function of position

[0255] p_(T)=Earth's radius of curvature at the GNSS positionPosition    LA_(T) = Latitude  LO_(T) = Longitude  TALT_(T) = altitude  Waypoint    WLA_(wT) = Waypoint  Lat.  WLO_(wT) = Waypoint  Lon.  WALT_(wT) = altitudePosition  X_(T) = ECEF  X  Y_(T) = ECEF  Y  Z_(T) = ECEF  Z  Waypoint  A_(T) = Waypoint  ECEF  X  B_(T) = Waypoint  ECEF  Y  C_(T) = Waypoint  ECEF  Z

Earth Radius of Curvature Determination

[0256] $\begin{matrix}{\rho_{w\quad T}:=\sqrt{\frac{\alpha^{2}}{1 - {e^{2} \cdot {\sin \left( {L\quad A_{w\quad T}} \right)}^{2}}}}} \\{{AT}\quad {WAYPOINT}}\end{matrix}\quad \begin{matrix}{\rho_{T}:=\sqrt{\frac{\alpha^{2}}{1 - {e^{2} \cdot {\sin \left( {L\quad A_{T}} \right)}^{2}}}}} \\{{{AT}\quad {GNSS}\quad {POSITION}}\quad}\end{matrix}$

Convert Trajectory to ECEF Coordinates

X _(T):=(TALT _(T)+ρ_(T))·cos(LA _(T))·cos(LO _(T))

Y _(T)=(TALT _(T)÷ρ_(T))·cos(LA _(T))·sin(LO _(T))

Z _(T) :=[TALT _(T)+ρ·(1−e²)]·sin(LA _(T))

Convert Waypoints to ECEF Coordinates

A _(wT):=(WALT _(wT)+ρ_(wT))·cos(WLA _(wT))·cos(WLO_(wT))

B _(wT):=(WALT _(wT)+ρ_(wT))·cos(WLA _(wT))·sin(WLO _(wT))

C _(wT) :=[WALT _(wT)+ρ_(wT)·(1−e²)]·sin(WLA _(wT))

Find Vector From Present Position to Next Waypoint

T=TIME OF TRAJECTORY DATA MATRIX INDEX

TIME INTO TRAJECTORY=61 SECONDS

Construct ECEF Waypoint Matrix Q

[0257] $Q:=\left\lbrack \quad \begin{matrix}A_{0} & B_{0} & C_{0} \\A_{N} & B_{N} & C_{N} \\A_{2 \cdot N} & B_{2 \cdot N} & C_{2 \cdot N} \\A_{3 \cdot N} & B_{3 \cdot N} & C_{3 \cdot N} \\A_{4 \cdot N} & B_{4 \cdot N} & C_{4 \cdot N} \\A_{5 \cdot N} & B_{5 \cdot N} & C_{5 \cdot N} \\A_{6 \cdot N} & B_{6 \cdot N} & C_{6 \cdot N} \\A_{7 \cdot N} & B_{7 \cdot N} & C_{7 \cdot N}\end{matrix}\quad \right\rbrack$

Waypoint Selection Criteria #1 Time Based Time Based Waypoint SelectionTechnique Determine Next Waypoint From Present Position

[0258]$G_{n}:={{until}\left\lbrack {{\left\lbrack \frac{T}{N \cdot \left( {1 + n} \right)} \right\rbrack - 1},{n + 1}} \right\rbrack}$

Waypoint Selection Criteria #2 Position Based Utilizes the Concept ofZones, See Zones

[0259] $Q = \left\lbrack \quad \begin{matrix}1491356.373377693 & {- 4435534.380128561} & 4319696.328998308 \\1491105.506082756 & {- 4434843.777395391} & 4320510.100123271 \\1491191.231021753 & {- 4434078.221408217} & 4321279.195524782 \\1491403.123106249 & {- 4433316.762941022} & 4322016.015673301 \\1491013.940737782 & {- 4432855.368457528} & 4322641.896808126 \\1490386.073951513 & {- 4432652.821583812} & 4323015.562834505 \\1489735.707050711 & {- 4432541.026386314} & 4323262.840511303 \\1489205.896384193 & {- 4432860.450400459} & 4322985.406680132\end{matrix}\quad \right\rbrack$

Determine Vector Between Previous and the Next Waypoint

Qa:=(Q _(a+1,0) −Q _(a,0) Q _(a+1,1) −Q _(a,1) Q _(a+1,2) −Q _(a,2))

PP:=(X _(T) Y _(T) Z _(T)) PRESENT POSITION

NWP:=[A _(N·(1+a)) B _(N·(1+a)) C _(N·(1+a))] NEXT WAYPOINT

TNWP:=NWP−PP VECTOR DISTANCE TO THE NEXT WAYPOINT

At Flight Time T=61 Seconds, the Next Waypoint is the Following X, Y, ZDistance From the Current Position

TNWP=(−394.0104406164 424.5394341322 588.6638708804)

Determine the Magnitude of the Distance to the Waypoint

DIST:={square root}{square root over ((TNWP ^(<0>)) ² +(TNWP ^(<1>)) ²+(TNWP ^(<1>)) ² )}

DIST:=825.8347966318 METERS

Next Determine if the Speed Should Remain the Same, or Change TimeExpected at Next Waypoint is 80 Seconds Into Trajectory Current Velocityis Based Upon GNSS Receiver Determination

[0260] ${VX} = \frac{{TNWP}^{< 0 >}}{80 - T}$

 VX=−20.7373916114 M/S X ECEF VELOCITY TO REACH WAYPOINT ON TIME

Compare Current X Velocity Required X Velocity, if Less Increase inVelocity, if Greater than Required Velocity Decrease Velocity

[0261] ${VY} = \frac{{TNWP}^{< 1 >}}{80 - T}$

 VY=22.3441807438 M/S Y ECEF VELOCITY TO REACH WAYPOINT ON TIME

Compare Current Y Velocity to Required Y Velocity, if less Increase inVelocity, if Greater than Required Velocity Decrease Velocity

[0262] ${VZ}:=\frac{{TNWP}^{< 2 >}}{80 - T}$

 VZ=30.9823089937 M/S Z ECEF VELOCITY TO REACH WAYPOINT ON TIME

Compare Current Z Velocity to Required Z Velocity, if less Increase inVelocity, if Greater than Required Velocity Decrease Velocity

VELECEF={square root}{square root over ((VX ²)−(VY ²)+(VZ ²))} VELOCITYMAGNITUDE

VELECEF=43.4649892964 M/S

VELECEF=(−20.737 22.344 30.982)

Determine the on Course off Course Navigational Data Unit VectorPerpendicular to Plane of QA and TNWP

[0263]${NP}:={{\frac{{Qa}^{T} \times {TNWP}^{T}}{{{Qa}^{T} \times {TNWP}^{T}}}\quad {NP}} = \begin{pmatrix}0.2375540749 \\{- 0.7054483132} \\0.6677654819\end{pmatrix}}$

Unit Vector Perpendicular to Plane of QA and NP

[0264]${UN}:={{\frac{{NP} \times {Qa}^{T}}{{{NP} \times {Qa}^{T}}}\quad {UN}} = \begin{pmatrix}{- 0.8621137731} \\{- 0.4698689823} \\{- 0.1896918074}\end{pmatrix}}$

Cross Track Error

XIRK:=UN·TNWP ^(T)

XTRK=28.5392020973

Calculate Cross Track Vector

VXTRK:=XTRK·UN

[0265]${VXTRK}:={{{{XTRK} \cdot {UN}}\quad {VXTRK}} = \left( \quad \begin{matrix}{\quad {- 24.6040392}} \\{- 13.4096858447} \\{\quad {- 5.4136528281}}\end{matrix} \right)}$

Unit Vector From Present Position to Next Waypoint

[0266]${UTNWP}:={{\frac{{TNWP}^{T}}{{TNWP}^{T}}\quad {UTNWP}} = \begin{pmatrix}{- 0.4771056417} \\0.514073076 \\0.7128106896\end{pmatrix}}$

Unit Vector of Present Position

[0267]${UPP}:={{\frac{{PP}^{T}}{{PP}^{T}}\quad {UPP}} = \begin{pmatrix}0.2341833314 \\{- 0.6961209085} \\0.6786559129\end{pmatrix}}$

Unit Vector of Next Waypoint

[0268]${UNWP}:={{\left( \frac{{NWP}^{T}}{{NWP}^{T}} \right)\quad {UNWP}} = \begin{pmatrix}0.2341210312 \\{- 0.6960529621} \\0.6787470933\end{pmatrix}}$

Check Against Great Circle Technique Great Circle Angleβ:=acos(UNVP·UPP) β·Ω=0.0074290102 Degrees Determine Range to NextWaypoint From Present Position h=0 Should be the Same as DIST When ALTis Nearly at Ellipsoid

[0269]${R3}:={\left( \left| {NWP}^{T} \middle| {+ \left| {PP}^{T} \right|} \right. \right) \cdot \frac{\beta}{2}}$R3 = 825.7511698494  METERS R3 − DIST = −0.0836267824  METERS

‘The ECEF Analysis Compares to Great Circle Analysis Very Closely’Converting Back to LAT. LON and MSL Determine Geodetic Parameters (LAT,LON & EL)

r:={square root}{square root over ((PP ^(<0>)) ² +(PP ^(<1>)) ² )}R:={square root}{square root over ((1−e²) ² ·r ²+(PP ^(<2>)) ² )}

[0270]$r:={{\sqrt{\left( {PP}^{< 0 >} \right)^{2} + \left( {PP}^{< 1 >} \right)^{2}}\quad R}:=\sqrt{{\left( {1 - e^{2}} \right)^{2} \cdot r^{2}} + \left( {PP}^{< 2 >} \right)^{2}}}$${s\quad \varphi}:=\sqrt{\frac{\left( {PP}^{< 2 >} \right)^{2}}{R^{2}}}$${RC}:={{\sqrt{\frac{\alpha^{2}}{1 - {{e^{2} \cdot s}\quad \varphi^{2}}}}\quad h}:={{\frac{R - {\left( {1 - e^{2}} \right) \cdot {RC}}}{1 - e^{2} + {{e^{2} \cdot s}\quad \varphi^{2}}}\quad h} = 287.6967718417}}$$\lambda:={{a\quad {\tan \left\lbrack \frac{\left( {PP}^{T} \right)_{1}}{\left( {PP}^{T} \right)_{0}} \right\rbrack}\quad \varphi}:={a\quad {\tan \left\lbrack \frac{\left( {PP}^{T} \right)_{2}}{r \cdot \left( {1 - e^{2}} \right)} \right\rbrack}\quad \begin{matrix}{{{\lambda \cdot \Omega} = {- 71.40645}}\quad} \\{{\varphi \cdot \Omega} = 42.930575339}\end{matrix}}}$

Convert to ENU Coordinates

[0271] ${ENU}:=\begin{bmatrix}{- {\sin (\lambda)}} & {\cos (\lambda)} & 0 \\{{- {\sin (\varphi)}} \cdot {\cos (\lambda)}} & {{- {\sin (\varphi)}} \cdot {\sin (\lambda)}} & {\cos (\varphi)} \\{{\cos (\varphi)} \cdot {\cos (\lambda)}} & {{\cos (\varphi)} \cdot {\sin (\lambda)}} & {\sin (\varphi)}\end{bmatrix}$

Find ENU Vector From Present Position to Next Waypoint East DistanceNorth Distance Up Distance

XYZ:=ENU·(TNWP ^(T() TNWP ^(<1>)))

[0272]${XYZ}:={{{{ENU} \cdot \left( {TNWP}^{T} \right)}\quad {XYZ}} = \begin{pmatrix}{- 238.0792858938} \\790.6424859464 \\14.3465805212\end{pmatrix}}$

East VEL. North VEL. Up VEL

VELENU:=ENU·(VELCEF^(T))M/S

[0273]${VELENU}:={{{{ENU} \cdot \left( {VELECEF}^{T} \right)}{M/S}\quad {VELENU}} = \begin{pmatrix}{- 12.5301751909} \\41.6123344504 \\0.7550895802\end{pmatrix}}$

 DISTENU:={square root}{square root over ((XYZ ₀)²+(XYZ ₁)²+(XYZ ₂)²)}

DIST=825.8347966318 METERS

VELENUMAG={square root}{square root over ((VELENU ₀)²+(VELENU₁)²+(VELENU ₂)²)}

VELENUMAG=43.4644892872 M/S

The ECEF Approach and the ENU Approach Produce the Same Results so it isPossible to use Either Coordinate Reference to Control the NecessarySpeed to the Waypoint Find True North Bearing Angle to Next WaypointUsing Tangent

[0274]${NBEAR}:={{a\quad {{\tan \left( \frac{{XYZ}_{0}}{{XYZ}_{1}} \right)} \cdot \Omega}\quad {NBEAR}} = {{- 16.7581666051}\quad {DEGREES}}}$

 NBEAR=−16.7581666051 DEGREES

Adjust for Trigonometric Quardrants and you have the True Bearing

[0275] Should the Range to the Waypoint become larger than the previousrange of the waypoint a waypoint may not have automatically indexed.This situation could occur if the vehicle did not get close enough tothe waypoint to index automatically or an ADS message may have beengarbled and the waypoint did not index, due to a lost ADS message. Inthis case the following analysis is performed:

[0276] a) temporarily increment the waypoint index

[0277] b) find the vector between the vehicles present position (PP) andthe next waypoint (NWP)

Vector to the next waypoint, TNWP=NWP(X,Y,Z)−PP(X,Y,Z)

[0278] c) Determine the current vehicle velocity vector

VEL=(VX,VY,VZ)

[0279] d) Determine the Dot Product between the Velocity Vector andVector TNWP

COSθ=TNWP dot VEL

[0280] e) If A <COS θ<B then keep current waypoint index

[0281] Where A and B are between 0 and 1 and represent an adjustablevalue based on the allowable vehicle velocity angular deviation from thetrue course

[0282] If −1<COS θ<=0 then return to previous waypoint index andgenerate wrong way alert the above technique can be expanded to includecurved approach, using cubic splines to smooth the transitions betweenwaypoints. A curved trajectory requires changes to the above set ofequations. Using the technique of cubic splines, one can calculate threecubic equations which describe smooth (continuous first and secondderivatives) curves through the three dimensional ECEF waypoints. Thefour dimensional capability is possible when the set of cubic equationsis converted into a set of parametric equations in time. The table belowdepicts an ECEF waypoint matrix which is used in cubic splinedeterminations.

[0283] TYPICAL WAYPOINT ECEF MATRIX

[0284] The AC&M processing utilizes the combination of precise ECEF X,Y, Z navigation and waypoints. Waypoints may be stored in a data filefor a particular runway approach, taxi path or departure path. Waypointsmay be entered manually, through the use of a data entry device. A listof waypoints describing a flight and or taxi trajectory is then assignedto a particular vehicle. To further supplement waypoint processingexpected arrival time may be added to each waypoint as well as velocityranges for each phase of flight. In this manner, 4 dimensional airportcontrol and management is provided utilizing a GNSS based system.Mathematical processing is used in conjunction with precise waypoints todefine flight trajectories. The mathematics typically uses cylindricalshapes but is not limited to cylinders, cones may also be used, and aredefined between adjacent waypoints. Typical on or off course processingis outlined below and is shown in FIG. 16.

EXAMPLE 1 Missed Waypoint, With off Course Condition

[0285] a. Construct the True Course line between the previous waypoint61 and the next waypoint 62

[0286] b. Determine the shortest distance (cross track error 64) fromthe current position 63 to the line 60 between the previous waypoint 61and next waypoint 62

[0287] c. Determine the magnitude of cross track error

[0288] d. Compare the magnitude of the cross track error to a predefinedlimit for total off course error shown as 65 in the figure.

[0289] e. Construct an mathematical cylindrical zone centered on theline between the previous 61 and next waypoint 62 with radius equal tothe off course threshold 65.

[0290] f. If the magnitude of the cross track error 64 is greater thanthe off course threshold 65 then raise flag and generate alert (offcourse).

[0291] g. Determine the necessary velocity to reach next waypoint onschedule, as shown previously

[0292] h. Is necessary velocity within preset limits or guidelines?

[0293] i. Check actual current velocity against preset limits andnecessary velocity, If above preset limits, raise flag and issue alertto slow down. If below preset limits, raise flag and issue alert tospeed up

[0294] j. Automatically index to the following waypoint 66 when theposition is within the index waypoint circle 67

[0295] k. Should wrong way be detected (positions 68 and 69), indexahead to the next to waypoint pair 66 and 62 and check direction oftravel 71 (Velocity) against the line 72 between the waypoints 66 and62, if the direction of travel is within a preset angular range 70 (A toB degrees) and not off course. If the check is true meaning not offcourse and headed towards next waypoint then index permanently towaypoint set 66 and 62, no alert generated

[0296] l. In the event that an off course condition and wrong way occur(position 69) a message is formatted which updates the layer filter forthe target which is off course, an alert is generated, the waypoints arereturned to the initial settings and action is taken to bring vehicleback on course possibly using a set of new waypoints

[0297] m. In the event of a velocity check which indicates that thespeed up or slow down velocity is outside of an approved range, generatea warning the speed for vehicle is out of established limits, Presetspeed over ground limits are adjusted for current air wind speed.

[0298] n. The controller reviews the situation displayed and ifnecessary invokes a navigational correction message to be sent to theReal Time Communication Handler, and then broadcast by radio to theaircraft off course or flying at the wrong speed. The controller at thistime may change the expected arrival time at the next waypoint if sonecessary

EXAMPLE 2 Missed Waypoint, With On Course Processing

[0299] a. Construct the True Course line between the previous waypoint66 and the next waypoint 72

[0300] b. Determine the shortest distance (cross track error 73) fromthe current position 74 to the line between the previous waypoint 66 andnext waypoint 72

[0301] c. Determine the magnitude of cross track error

[0302] d. Compare the magnitude of the cross track error to a predefinedlimit for total off course error shown as 75 in the figure.

[0303] e. Construct an mathematical cylindrical zone centered on theline between the previous waypoint 66 and next waypoint 72 with radiusequal to the off course threshold 75

[0304] f. If the magnitude of the cross track error 73 is greater thanthe off course threshold 75 then raise flag and generate alert (offcourse).

[0305] g. Determine the necessary velocity to reach next waypoint onschedule, as shown previously

[0306] h. Is necessary velocity within preset limits or guidelines?

[0307] i. Check actual current velocity against preset limits andnecessary velocity, If above preset limits, raise flag and issue alertto slow down. If below preset limits, raise flag and issue alert tospeed up

[0308] j. Automatically index to the following waypoint 76 when theposition is within the index waypoint circle 77

[0309] k. Should wrong way be detected (position 74), index ahead to thenext to waypoint pair 76 and 72 and check direction of travel 78(Velocity) against the the line 80 between the waypoints 76 and 72, ifthe direction of travel is within a preset angular range 79 (A to Bdegrees) and not off course. If the check is true meaning not off courseand headed towards next waypoint then index permanently to waypoint set76 and 72, no alert generated

[0310] l. In the event of a velocity check which indicates that thespeed up or slow down velocity is outside of an approved range, generatea warning the speed for vehicle is out of established limits, Presetspeed over ground limits are adjusted for current air wind speed.

[0311] m. The controller reviews the situation displayed and ifnecessary invokes a navigational correction message to be sent to theReal Time Communication Handler, and then broadcast by radio to theaircraft off course or flying at the wrong speed. The controller at thistime may change the expected arrival time at the next waypoint if sonecessary

[0312] The AC&M processing performs all on or off course processingdeterminations and the displays information related to on or off courseor late or early arrival conditions.

[0313] ALERT DISPLAY FUNCTION

[0314] Within the AC&M system collision alerts, zone, off course andimproper speed warnings are handled somewhat differently than normalposition updates. When the AC&M processing recognizes a warningcondition, the aircraft(s)/vehicle(s) involved are moved to a specialALP layer. The layer filter controls what graphic parameters aparticular vehicle or aircraft is displayed with. The change in thelayer from the default vehicle layer signifies that the target has beenclassified as a potential collision, zone intrusion risk, off coursecondition or improper speed.

[0315] AC&M CONTROL ZONES

[0316] ATC Control Zones are used to sort and manage air and surfacetraffic within the airport space envelope. the AC&M Control Area isdivided into AC&M Control Zones. Typically the outer most airportcontrol zone interfaces with an en route zone. Aircraft within the 3-DAC&M zone transmit their GNSS derived positions via an on boarddatalink. The GNSS data is received by the airport AC&M equipment. TheAC&M Processing determines the ECEF AC&M Control Zone assignment basedon the aircraft's current position and assigns the aircraft to the maplayer associated with that Control Zone. Mathematical computations asdefined previously, are used to determine when a vehicle is in aparticular control zone.

[0317] As an aircraft enters the AC&M or transitions to another ATCControl Zone, a handoff is performed between the controllers passing andreceiving control of that aircraft. Surface traffic is handled in thesame manner. With this AC&M scenario, each controller receives alltarget information but suppresses those flyers that are not under hiscontrol. In this manner the controller or operator views on thosevehicles or aircraft in his respective control zone. Should there be acollision condition across an ATC zone boundary the conflicting vehicleswill be displayed in a non-surpressable layer.

[0318] All targets within an AC&M Control Zone would be placed in theappropriate map layer for tracking and display purposes. Layer codingfor each tracked target can be used to control graphic displayparameters such as line type, color, line width as well as be used as akey into the underlying database for that object.

[0319] Additional AC&M Control Zones may be defined for other surfaceareas of the airport, such as construction areas, areas limited tospecific type of traffic, weight limited areas and others. These areasmay be handled through ATC but will most or be controlled by airline orairport maintenance departments. the concept of a zone based AC&M systemintegrated with 3-D map information provides a valuable management andnavigational capability to all vehicles and aircraft within the airportspace envelope.

[0320] ENTERING WAYPOINTS

[0321] The AC&M processing defined herein allows the user to enterwaypoints using the digital map as a guide. To enter a series ofwaypoints the controller simply uses the map which may provide plan andside views of the airport space envelope. The cursor is moved to theappropriate point and a selection is made by pressing a key. Theposition is then stored in a list with other waypoints entered at thesame time. The user is then prompted to enter a name for the waypointlist and an optional destination. Lastly, the waypoints converted theappropriate coordinate frame and are then saved to a file or transmittedto a particular vehicle. In this manner the user may add and definewaypoints.

[0322] DEFINING ZONES

[0323] The user may define zones using the digital map as a guide. Toenter a series of zones the controller simply uses the map which mayprovide plan and side views of the airport space envelope. The cursor ismoved to the appropriate point and a selection is made by pressing akey. The position is then stored in a list with other zone definitionpoints. The controller is then prompted to enter a name for the zone(pole, tower, construction area, etc.) and type of zone (circle, sphere,box, cylinder, etc.). Lastly, the zones are converted to the appropriatecoordinate frame and saved to a file or transmitted to a particularvehicle. In this manner the user may define additional zones.

[0324] The ability to quickly and accurately define zones is key to theimplementation of a zones based AC&M capability.

[0325] ADS MESSAGE FORMAT CONSIDERATIONS

[0326] The definition and standardization of a ‘seamless’ aviationsystem datalink format(s) is critical to the implementation of aGNSS-based aviation system.

[0327] SAMPLE ADS MESSAGE FORMAT

[0328] Perhaps the most basic issue which must be resolved in thedetermination of the datalink format, is the selection of the coordinatesystem and units for the GNSS-derived position and velocity data.Compatibility with digital and paper maps, navigation system and overallmathematical processing efficiency play major roles in the selection ofthe coordinate reference.

[0329] Below is a list of criteria which are used in this determination:WORLD WIDE USE The coordinate reference system is recognized throughoutthe world. Scale does not change as a function of where you are on theearth. SIMPLE NAVIGATION The coordinate system lends itself to simplevector navigational MATHEMATICS mathematics. COMPATIBLE WITH Thecoordinate reference can support curved trajectory COMPLEX 4-D CURVEDmathematics. PATH 4-D NAVIGATION FUNCTIONS COMPATIBLE WITH Is compatiblewith management operations at ATC and aboard MANAGEMENT SYSTEM A/Vs.COMPATIBLE WITH SPACE The coordinate system is compatible with low earthorbit or OPERATIONS space-based operations. NAD83 AND WGS84 REF. Thereference system is compatible with NAD 83 and WGS 84 SINGLE ORIGIN Thesystem has one single point origin. LINEAR SYSTEM The system is a linearcoordinate system and does not change scale as a function of location.UNITS OF DISTANCE The coordinate system is based on units of distancerather than angle NO DISCONTINUTITIES The coordinate reference system iscontinous world wide.

[0330] The ECEF X, Y, Z Cartesian coordinate system satisfies all of theabove criteria. Other systems may be used such as, Universal TransverseMercator, Latitude, Longitude and Mean Sea Level and other grid systemsbut additional processing overhead and complexities are involved.

[0331] A representative ADS message structure is provided below: SAMPLEAIRPORT ECEF MESSAGE CONTENT ID# 8 Characters VEHICLE TYPE 4 CharactersCURRENT POSITION: ECEF X Position (M) 10 Characters ECEF Y Position (M)10 Characters ECEF Z Position (M) 10 Characters ECEF X2 Position (M) 4Characters * ECEF Y2 Position (M) 4 Characters * ECEF Z2 Position (M) 4Characters * ECEF X3 Position (M) 4 Characters * ECEF Y3 Position (M) 4Characters * ECEF Z3 Position (M) 4 Characters * ECEF X Velocity (M/S) 5Characters ECEF Y Velocity (M/S) 5 Characters ECEF Z Velocity (M/S) 5Characters NEXT WAYPOINT (WHERE HEADED INFORMATION): ECEF X 10Characters ECEF Y 10 Characters ECEF Z 10 Characters TIME 8 Characters

[0332] A bit oriented protocol, representing the same type ofinformation, may be used to streamline operations and potential errorcorrection processing. (The asterisks denote optional fields which maybe used to determine the attitude of an aircraft.)

[0333] The individual fields of the ADS message are described below:

ID(8 Character Word, Alpha-numeric)

[0334] The ID field is used to identify the particular vehicle oraircraft. For aircraft this is typically the flight number or, in thecase of GA or private aircraft, the tail number. For airport surfacevehicles it is the vehicle's callsign.

Type of Vehicle (4 Character Word, Alpha-numeric)

[0335] The vehicle type is used to identify the A/V's typeclassification. Numerous type classifications may be defined tocategorize and identify various aircraft and surface vehicles.

Current ECEF X,Y,Z Position (10 Characters by 3 Words)

[0336] The ECEF X,Y,Z position fields provide the vehicle's position atthe time of the ADS transmission in ECEF X,Y,Z coordinates. The positionis calculated by the GPS receiver. Based on the system design, thesevalues may or may not be smoothed to compensate for system latencies.The message length of 10 characters provides a sign bit in the mostsignificant digit and 9 digits of positional accuracy. The leastsignificant digit represents 0.1 meter resolution. This provides amaximum ADS distance of +9999999.9 which translates to an altitude ofabout 3600 KM above the earth's surface, providing sufficient coverageto support low earth orbiting satellites and spacecraft.

Delta Positions (Relative Positions, 4 Characters by 6 Words)

[0337] Delta positions are used to represent the positional offset oftwo other GPS antenna locations. These locations can be used todetermine the attitude of the aircraft or its orientation when it is notmoving. All delta distances are calculated with respect to the currentECEF position. Straight forward ECEF vector processing may then be usedto determine the attitude and orientation of the aircraft with respectto the ECEF coordinate frame. An ECEF-to-local on board coordinatesystem (ie. North, East, Up) conversion may be performed if necessary.Accurate cross wind information can be determined on the ground and onboard the aircraft from delta position information. Delta positions mayalso be used as 3-D graphical handles for map display presentations.

[0338] The message length of 4 characters provides a sign bit in themost significant digit and 3 digits of delta position accuracy. Theleast significant digit represents 0.1 meter resolution.

ECEF X,Y,Z Velocity (5 Characters by 3 Words)

[0339] The fields represent the A/V's ECEF X,Y,Z velocity in meters persecond. Tenth of a meter/second resolution is required during the groundphase of GPS based movement detection, latency compensation, zone andcollision detection processing.

[0340] The message length of 5 characters provides a sign bit in themost significant digit and 4 digits of velocity accuracy.

Next Waypoint (10 Characters by 3 Words)

[0341] These fields describe where the A/V is currently headed, in termsof the ECEF X,Y,Z coordinates of the next waypoint. This provides intentinformation which is vital to the collision avoidance functions.

Time (Universal Coordinated Time) 8 Characters

[0342] This field identifies the Universal Coordinated Time at the timeof the ADS transmission. This time is the GPS derived UTC time (inseconds) plus any latency due to processing delays (optional). The ADSmessage format provides a very valuable set of information thatsimplifies mathematical processing. Since the ECEF Cartesian coordinateframe is native to every GPS receiver, no additional GPS burden isincurred. This type of ADS broadcast message information is more thanadequate for precision ground and air operations as well as for generalATC/airport control and management functions.

[0343] OVERVIEW OF CANDIDATE ADS ARCHITECTURES

[0344] Many communication technologies are available which can provideADS capability. Many of the systems already exist in some form today,but may require modification to meet the requirements of ADS in theterminal area. In evaluating datalink candidates, it is important thatfuture airport standards are not compromised by forcing compatibilitywith the past. Systems should develop independently in a manner designedto achieve the systems' maximum operational benefits. Transitionalelements and issues of compatibility with current systems are betterhandled through the implementation of translators which do not detractfrom a future system's true potential.

Mode S Interrogation

[0345] The Mode S system is in use today and is compatible with today'sen route radar and Terminal Radar Approach Control (TRACON)-based airtraffic control systems. Current Mode S 1030 MHZ interrogation isperformed using Mode S radars which scan at the 4.8 second rate. Thescan rate represents the rotational period of the scanning antenna. Whena target is interrogated by the radar pulse, the aircraft or vehiclebroadcasts its GPS-based information to air traffic control at 1090 MHZ.In this manner, ADS information is received by ATC and by otherinterrogating sources.

[0346] Numerous problems exist with any interrogation technique whichhas multiple interrogators. For radar systems to provide seamlesscoverage, surface, parallel runway and airport surveillance radars arerequired. Aircraft and surface vehicles would require the use of atransponder which broadcasts a response at 1090 MHZ when interrogated at1030 MHZ. In an environment where multiple interrogations are required,system complexities crease dramatically. Early ATCRBS, Mode A and Mode Csystems were troubled with too many unsynchronized interrogationrequests. This resulted in cross talk, garble and loss of transmissionbandwidth. Further complicating the airport environment is thepossibility of reflected signals which interrogate areas of the airportoutside the view of the surveillance radar. This clogs the 1090 channeland further complicates surveillance processing. Airborne Mode Stransponder operation requires that squitter messages be broadcast whenin the air and turned off on the ground. A Mode S squitter is a periodicrepetitive broadcast of ADS information. This, by definition, willinterfere with airport interrogation broadcasts and essentially create aself jamming system.

[0347] Any airport ADS system utilizing a Mode S interrogationcapability would require almost a ground up development effortencompassing the myriad of necessary surveillance systems.

Mode S Squitter (GPS Squitter)

[0348] Similarly, the Mode S squitter utilizes the Mode S frequencies. Asquitter is a randomly timed broadcast which is rebroadcastperiodically. The Mode S squitter broadcasts GPS information at aperiodic rate at 1090 MHZ with a bit rate of 1 MBPS. Current thinkingrequires that the ADS system be compatible with the Traffic CollisionAvoidance System (TCAS). The TCAS system currently uses a 56 bitsquitter message that must be turned off in the low altitude airportenvironment since it will interfere with other radar processingactivities performed on the ground. Turning TCAS off inside the terminalarea (where most midair problems and airport surface collisions occur)defeats the system's operational benefits where they are needed most.Operationally this is unacceptable.

[0349] A modified 112 bit squitter message has been proposed by MITLincoln Laboratories. With this approach, the GPS data is squitteredtwice per second to support ground and low altitude operations. Theproposed Mode S squitter operation has distinct advantages over the ModeS interrogation method. Broadcasts are generated from all aircraft and(potentially) surface vehicles. Message collisions are possible,especially when the number of users is increased. If a collision occurs,the current message is lost and one must wait for the next message to betransmitted. At a two hertz transmission rate, this is not a significantproblem. Analysis performed by MIT Lincoln Laboratories indicates thatan enhanced Mode S squitter has potential to support operations at majorairports.

[0350] The integration of the Mode S Squitter, as currently defined, isnot without risk. This implementation requires a fleet update to convertto the 112 bit fixed format. Procedural issues of the switch-overbetween the 56 and 112 bit operation remain problematic. Operation inmetroplex areas such as New York may create operationally dangerousconditions. Airside TCAS and ASR 56 bit transponder responses would beturned off based on phase of flight to be compatible with 112 bitsquitter messages used at low altitudes and on the ground. In metroplexareas, confusion is almost certain for both the pilot and air trafficcontroller when systems are turned off and on. Further modifications maybe required to ground and vehicular equipment should these issues be asignificant problem.

[0351] The 112 bit fixed squitter length message, as defined in May1994, fails to take advantage of precise GNSS Velocity information. Thisis a significant limiting factor in the proposed squitter messageformat. The current squitter message is designed to be compatible withtoday's radar processing software and is not designed to fullycapitalize on GNSS and ADS capabilities.

Aviation Packet Radio (AVPAC)

[0352] AVPAC radio is currently in use with services provided by ARINCand may be a viable candidate to provide ADS services. Again, aGPS-based squitter or an interrogator-initiated broadcast is utilized ataeronautical VHF frequencies. Work is underway to adapt AVPAC to supportboth voice and data transmissions. A Carrier Sense Multiple Access(CSMA) protocol is utilized on multiple VHF frequencies

Aircraft Communications Addressing & Reporting System

[0353] Another communication system currently in use by the aviationindustry is ACARS. ACARS is a character oriented protocol and currentlytransmits at 2400 baud. Work is underway to increase the baud rate tosupport more complex message formats.

VHF/UHF Time Division Multiple Access (TDMA)

[0354] An interesting communication scheme currently under test anddevelopment in Sweden utilizes TDMA operation. TDMA is similar tocommunication technologies used by the United States military andothers. In this system, each user is assigned a slot time in which tobroadcast the ADS message. A single or multiple frequency system may beutilized based upon total traffic in the area. Upon entering an airportarea, the user equipment listens to all slot traffic. The user equipmentthen selects an unused broadcast time slot. Precise GPS time is used todetermine the precise slot. ADS broadcasts are then transmitted at aperiodic rate. Broadcasts typically repeat at one second intervals.Should a collision be detected upon entering a new location, the systemthen transmits on another clear time slot. Since all time slots arecontinuously received and monitored, all necessary information forsituational awareness and collision avoidance is available.

[0355] This system maximizes the efficiency of the broadcast link since,in a steady state environment, no transmission collisions can occur. Atime guard band is required to assure that starting and endingtransmissions do not overlap. The size of the guard band is a functionof GPS time accuracy and propagation delay effects between various usersof the system. Another feature of this system is an auto-rangingfunction to the received broadcasts. This is possible due to the factthat the ADS slot transmissions are defined to occur at precise timeintervals. It is then possible, using a GNSS synchronized precise timesource, to determine the transit time of the ADS broadcast. Bymultiplying the speed of light by the transit time, one may calculatethe 1-dimensional range to the transmitting object. In reality, a moreprecise direction, distance and predicted future location is obtainablefrom the ADS message information itself.

Code Division Multiple Access (CDMA) Spread SPrectrum

[0356] CDMA spread spectrum ADS broadcasts utilize a transmission formatsimilar to that used in the GPS satellites. PRN codes are utilized touniquely identify the sending message from other messages. The number ofusers able to simultaneously utilize an existing channel depends uponthe PRN codes used and the resulting cross correlation function betweenthe codes. This implementation is being utilized commercially inwireless computer systems with data rates exceeding 256 KBPS. In afrequency agile environment, this implementation may be able to providesecure ADS services.

Cellular Telephone

[0357] Cellular technology is rapidly changing to support the largepotential markets of mobile offices and personal communication systems.CCITT and ISDN standards will provide both voice, video and datacapability. Cellular communication may be used by surface vehicles andaircraft for full duplex data link operations. ADS broadcast messageformats receivable by ATC and other users will require changes tocommercially available services. Cellular telephone has the mass marketadvantage of cost effective large scale integration and millions ofusers to amortize development costs over. This particular technologyholds promise, and bears watching.

[0358] As the above examples show, a number of datalinks exist or may bemodified to provide ADS services. It is not the intent of thisspecification to rigidly define a particular datalink.

[0359] ADS OPERATIONAL CONSIDERATIONS

[0360] To fully exploit the ADS concepts presented in thisspecification, a new set of operational procedures and processingtechniques are necessary. The ADS concept will provide the controllerand the Aircraft/Vehicle (A/V) operator with the best possible view ofthe airport environment. With highly accurate 3-D position and velocityinformation, many new operational capabilities are possible which willprovide increased efficiency and safety improvements. The followingsections show how precise ADS information is used in seamless airportcontrol and management.

[0361] DEFINITION OF COMPATIBLE WAYPOINTS

[0362] Waypoints based upon the precise 3-D map and standard surface,approach and departure paths are used for surface and air navigation inthe 3-D airport space envelope. Waypoints may be stored in a variety ofcoordinate systems, such as conventional Latitude, Longitude, Mean SeaLevel; State Plane Coordinates; ECEF X, Y, Z; and others. Thenavigational waypoint and on/off course determinations are preferred tobe performed in an ECEF X, Y, Z coordinate frame, but this is notmandatory.

[0363] Waypoints and navigation processing should be defined anddesigned for compatibility with air and ground operations, includingprecision approach capability. The same information and processingtechniques should be in place on board the ANV's and at the AC&M. TheAC&M performs mirrored navigational processing using the same coordinatereferences and waypoints as those on board the A/Vs. In this manner, theAC&M system can quickly detect off course and ‘wrong way’ conditionsanywhere in the 3-D airport space envelope at the same time theseconditions are detected on board the A/V's.

[0364] WAYPOINT NAVIGATION MATHEMATICS

[0365] The following mathematical example is provided to show howwaypoints and trajectories are processed in the ECEF X, Y, Z coordinatereference frame. An actual DGPS flight trajectory is used for thismathematical analysis. The flight trajectory and waypoints have beenpreviously converted to an ECEF X, Y, Z format.

[0366]FIG. 11 presented in the earilier ON Or Off Course Processingsection depicts the major ECEF waypoint elements which are usedthroughout the following navigation mathematical processing example.

[0367] The following example utilizes an ECEF Waypoint Matrix. In thisexample, the next waypoint (NWP) is element 5 in the matrix and theprevious waypoint (PWP) is element 4. The values for the waypoints areshown in the examples. The range to the waypoint is determined from thecurrent position. The range is compared to the previous range forpossible off course or wrong way conditions. If the range is increasing,the waypoint auto-indexing distance may have been exceeded even thoughthe vehicle is on course. In this situation, the waypoint index istemporarily indexed and checking is performed to determine whether thevelocity vector is pointing within X degrees of the next waypoint (inthis example it is set to +/−90 degrees). Based upon the outcome, awrong way signal is generated or the waypoints are indexed. The ECEFcross track vector (XTRK) is determined and projected on to the verticalaxis, local lateral axis and the plane tangent with the earth's surfaceat the current position. $\begin{matrix}\begin{matrix}{{CONSTRUCT}{\quad \quad}{TRAJECTORY}\quad {VECTOR}} \\{{OF}\quad {PRESENT}\quad {POSITION}\quad ({PP})}\end{matrix} & \begin{matrix}{{INDEX}\quad {TO}} \\{{NEXT}\quad {WAYPOINT}}\end{matrix} \\\quad & {i:=1} \\{{PP}^{< t >}:=\begin{bmatrix}x_{t} \\y_{t} \\z_{t}\end{bmatrix}} & \quad \\{{PRESENT}\quad {POSITION}} & {{WAYPOINT}\quad {INDEX}} \\{{PP}^{< t >}:=\begin{pmatrix}1490699.03159201 \\{- 4432742.69262449} \\4322846.19931227\end{pmatrix}} & {{wpin}_{i}:={{floor}\left( \frac{t}{n} \right)}}\end{matrix}$ $\begin{matrix}{{ECEF}\quad X} & {{ECEF}\quad Y} & {{ECEF}\quad Z}\end{matrix}$ ${WP} = \begin{bmatrix}1491356.37337769 & {- 4435534.38012856} & 4319696.32899831 \\1491105.50608276 & {- 4434843.77739539} & 4320510.10012327 \\1491191.23102175 & {- 4434078.22140822} & 4321279.19552478 \\1491403.12310625 & {- 4433316.76294102} & 4322016.0156733 \\1491013.94073778 & {- 4432855.36845753} & 4322641.89680813 \\1490386.07395151 & {- 4432652.82158381} & 4323015.56283451 \\1489735.70705071 & {- 4432541.02638631} & 4323262.8405113 \\1489205.89638419 & {- 4432860.45040046} & 4322985.40668013 \\1488862.17692919 & {- 4433298.26186174} & 4322564.11714943 \\1488577.40869804 & {- 4433715.22689756} & 4322248.17133335 \\1488250.73266894 & {- 4434298.26191826} & 4321864.00370927\end{bmatrix}$

PWP := (WP_(pwp, 0)  WP_(pwp, 1)  WP_(pwp, 2))${PWP}^{T} = \begin{pmatrix}1491013.94073778 \\{- 4432855.36845753} \\4322641.89680813\end{pmatrix}$

NWP := (WP_(nwp, 0)  WP_(nwp, 1)  WP_(nwp, 2))${NWP}^{T} = \begin{pmatrix}1490386.07395151 \\{- 4432652.82158381} \\4323015.56283451\end{pmatrix}$

BWP := NWP^(T) − PWP^(T) ${BWP} = \begin{pmatrix}{- 627.8667862699} \\202.5468737194 \\373.6660263799\end{pmatrix}$

Distance Between the Waypoints

|BWP|=758.2006572307

[0368] TNWP := NWP^(T) − PP^( < t>) ${TNWP} = \begin{pmatrix}{- 312.9576405} \\89.8710406795 \\169.36352224\end{pmatrix}$

Distance to the Waypoint (Range)

|TNWP|=367.019470009

[0369] CHECK RANGE TO SEE IF A WAYPOINT HAS BEEN MISSED

[0370] IF VEH. N RANGE>PREVIOUS VEH. N RANGE THEN

[0371] PERFORM TEST:

[0372] INCREMENT WAYPOINT INDEX

[0373] FIND THE VECTOR LINE BETWEEN THE CURRENT POSITION AND

[0374] NEXT WAYPOINT

TNWP=NWP(X,Y,Z)−PP(X,Y,Z)

[0375] CALCULATE ECEF CURRENT POSITIONS VELOCITY VECTOR

VEL=(VX,VY,VZ)

[0376] CALCULATE DOT PRODUCT BETWEEN THE VELOCITY VECTOR AND TNWP

COS θ=TNWP(X,Y,Z) dot VEL(VX,VY,VZ)

|TNWP|=SRT[(X*X)+(Y*Y)+(Z*Z)]

|VEL|=SRT[(VX*VX)+(VY*VY)+(VZ*VZ)]

COS θ=[(X*VX)+(Y*VY)+(Z*VZ)]/(|TNWP|*|VEL|)

[0377] IF 0<COS θ<1 THEN KEEP CURRENT WAYPT INDEX,

[0378] MISSED AUTO WAYPOINT INDEX DISTANCE

[0379] IF −1<COS θ<=0 THEN GO BACK TO PREVIOUS WAYPOINT FLASH WRONG WAY$\begin{matrix}{{PRESENT}\quad {POSITION}} & {{NEXT}\quad {WAYPOINT}} \\{{PP}^{< t >} = \begin{pmatrix}1490699.03159201 \\{- 4432742.69262449} \\4322846.19931227\end{pmatrix}} & {{NWP}^{T} = \begin{pmatrix}1490386.07395151 \\{- 4432652.82158381} \\4323015.56283451\end{pmatrix}} \\\begin{matrix}\begin{matrix}\begin{matrix}{{{UNIT}\quad {VECTOR}\quad {PERPENDICULAR}}\quad} \\{{TO}\quad {PLANE}\quad {CONTAINING}\quad {INTER}\text{-}}\end{matrix} \\{{{{SECTING}\quad {LINES}\quad {TNWP}}\quad\&}\quad {LINE}}\end{matrix} \\{{BETWEEN}\quad {WAYPOINTS}}\end{matrix} & \begin{matrix}\begin{matrix}{{UNIT}\quad {NORMAL}\quad {FROM}} \\{{DESIRED}\quad {TRACK}\quad {TO}\quad {THE}}\end{matrix} \\{{PRESENT}\quad {POSITION}\quad {POINT}}\end{matrix} \\{{NP}:=\frac{{BWP} \times {TNWP}}{{{BWP} \times {TNWP}}}} & {{UN}:=\frac{{NP} \times {BWP}}{{{NP} \times {BWP}}}} \\{{NP} = \begin{pmatrix}0.0568495318 \\{- 0.8345970318} \\0.547919634\end{pmatrix}} & {{UN} = \begin{pmatrix}{- 0.557688735} \\{- 0.4817501474} \\{- 0.6759438367}\end{pmatrix}}\end{matrix}$

Determine the Adjusted Position

[0380] The adjusted position is the point, on the line between theprevious and next waypoint which is normal to the present position.ADJ^( < t>) := PP^( < t>) + VXTRK ${ADJ}^{< t >} = \begin{pmatrix}1490689.686215317 \\{- 4432750.765472868} \\4322834.872295278\end{pmatrix}$

Determine the Unit Vector in the Direction From Center of Mass of theEarth to Adjusted Position

[0381] This vector is in the local vertical direction and for allpractical purposes in the vertical direction at the actual userposition, since the separations are very small compared to the length ofthe vector. ${UVADJ}:=\frac{{ADJ}^{< t >}}{{ADJ}^{< t >}}$${UVADJ} = \begin{pmatrix}0.234070768 \\{- 0.696038475} \\0.6787792844\end{pmatrix}$

Find the Projection of the XTRACK Vector on to the Unit Vector

[0382] This distance represents the vertical distance to true course

VERTDIST:=VXTRK·UVADJ VERTDIST−4.2570109135

Find the Lateral Axis of XTRK Information

[0383] The lateral axis represents horizontal distance to true coursefrom the current position. A number of steps are necessary in thisdetermination and are outlined below.${UVPER}:=\frac{{VXTRK} \times {ADJ}^{< t >}}{{{VXTRK} \times {ADJ}^{< t >}}}$${UVPER} = \begin{pmatrix}{- 0.8245345664} \\0.2278021297 \\0.5179275418\end{pmatrix}$

Find the Vector (VLAT) Which Lies in the Plane Formed by UVADJ and VXTRKWhich is Perpendicular to the UVADJ Vector it is Known That VLAT DOTUVADJ=0 and UVPER DOT VLAT=0 Solve for VLAT by Using SimultaneousEquations Equation #1

[0384] $\begin{matrix}{{{UVADJ}\quad \underset{0}{VL}{AT}\quad \underset{0}{+ \quad U}{VADJ}\quad \underset{1}{V}{LAT}\underset{1}{\quad {+ \quad U}}{VADJ}\quad \underset{2}{V}{LA}\underset{2}{T =}\quad 0}} & {{EQUATION}\quad {\# 1}} \\{{UVPER}\quad \underset{0}{VL}{AT}\underset{0}{\quad {+ \quad U}}{VPER}\quad \underset{1}{VL}{AT}\underset{1}{\quad {+ \quad U}}{VPER}\quad \underset{2}{VL}A\underset{2}{{T =}\quad}0} & {{EQUATION}\quad {\# 2}}\end{matrix}$

[0385] Substitute and Solve in Terms of Vlat₂$\frac{{UVADJ}_{0}}{{UVPER}_{0}} = {{{- 0.2838822986}\quad \frac{{UVADJ}_{1}}{{UVPER}_{1}}} = {- 3.0554520095}}$

Define Variables for Equation Substitution

[0386]${VLATX} = \frac{{\left( \frac{- {UVADJ}_{1}}{{UVPER}_{1}} \right) \cdot {UVPER}_{2}} + {UVADJ}_{2}}{{\left( \frac{{UVADJ}_{1}}{{UVPER}_{1}} \right) \cdot {UVPER}_{0}} - {UVADJ}_{0}}$${VLATY} = \frac{{\left( \frac{- {UVADJ}_{0}}{{UVPER}_{0}} \right) \cdot {UVPER}_{2}} + {UVADJ}_{2}}{{\left( \frac{{UVADJ}_{0}}{{UVPER}_{0}} \right) \cdot {UVPER}_{1}} - {UVADJ}_{1}}$

Define VLAT Vector

[0387] NOTE: VLAT(Z) TERM WILL CANCEL OUT WHEN FINDING UNIT VECTOR

VLAT:=(VLATX VLATY 1) VLAT=(0.989509706 1.3079658867 1)${UVLAT} = {{\frac{VLAT}{\sqrt{{VLATX}^{2} + {VLATY}^{2} + 1^{2}}}\quad {UVLAT}^{T}} = \begin{pmatrix}0.5151248629 \\0.6809086804 \\0.5205859627\end{pmatrix}}$

Perform Check to See if UVLAT is Perpendicular to UVADJ

UVADJ·UVLAT ^(T)=5.5511151231·10⁻¹⁷

Close Enough to Zero Is Perpendicular Perform Check to See if UVLAT isPerpendicular to UVPER

UVPER·UVLAT ^(T=)0

It is Perpendicular Project the Cross Track to the Lateral Axis

[0388] The sign of the lateral distance (LATDIST) and vertical distance(VERTDIST) determine whether one turns right or left or goes up or downto true course

[0389] From a simplicity standpoint, the ECEF coordinate frame providesdirect GPS compatibility with minimal processing overhead. The system isbased upon the ECEF world wide coordinate frame and provides for 4-Dgate-to-gate navigation without local coordinate referencecomplications. Furthermore, it is directly compatible with zoneprocessing functions as described in earlier sections.

[0390] The above techniques can also be expanded to include curvedapproaches using cubic splines to smooth the transitions betweenwaypoints. A curved trajectory requires changes to the above set ofequations. Using cubic splines, one can calculate three cubic equationswhich describe smooth (continuous first and second derivatives) curvesthrough the 3-D ECEF waypoints. Additional information on the use ofsplines may be found in mathematical and numerical programming textbooks. Four dimensional capability is possible when the set of cubicequations is converted into a set of parametric equations in time.

[0391] DISPLAY GRAPHICS AND COORDINATED REFERENCES

[0392] Three dimensional display graphics, merged with GPS sensorinputs, provide exciting new tools for airport navigation, control andmanagement. Today's airport users operate in a 4dimensional environmentas precisely scheduled operations become increasingly important in anexpansion-constrained aviation system. The 4-D capability of GPSintegrated with precise 3-D airport maps and computer graphics, provideseamless airport safety and capacity enhancements. The merger of thesetechnologies provides precise, real-time, 3-D situational awarenesscapability to both the ANV operators and the air traffic controller.

[0393] The FIG. 17 shows a missed approach 81 on runway 35 followed by atouch and go 82 on runway 24 at the Manchester Airport. The power ofsuch a situation display 83 presentation for the air traffic controllercan be instantly recognized. Upon closer inspection, it becomesincreasingly clear that GPS and precise graphical maps can be a valuableasset in air and ground navigation.

[0394] For the air traffic controller, 3-D situational awarenessdisplays, supplemented with navigation status information, aresufficient. For the pilot navigating in a 3-D world, a 3-D terrain orairport map superimposed with graphical navigational information wouldbe extremely valuable, particularly in adverse weather conditions.

[0395] The FIG. 18 combines the elements of precise ECEF navigationalinformation with a 3-D airport map. The key element in the constructionof the map is compatibility with the navigation display, where theselection of map and navigation coordinate frames is of paramountimportance. Upon inspection of computer graphical rotation andtranslational matrices, it becomes clear that, for processing speed andmathematical efficiency, the Cartesian coordinate system is preferredfor the map database. A 3-D X,Y,Z digital map presentation provides themost efficient path to 2-D screen coordinates through the use ofprojection transformations.

[0396] The integration of GPS-based navigation information with digitalmaps suggests that new methods of navigation processing should beconsidered. In the past, aircraft typically relied on a signal in spacefor instrument-based navigation. The instrument landing system (ILS)consists of a localized directed signal of azimuth and elevation. theVOR-DME navigation system uses a signal in space which radiates from anantenna located at a particular latitude and longitude. Altitude isdetermined from pressure altitude. Current, 2-D radar surveillancesystems are also based upon a localized coordinate reference, usually tothe center of the radar antenna. Again, altitude information is frombarometric pressure readings which vary with weather. The integration oflocalized navigation and surveillance systems and 3-D ATC andnavigational display presentations require an excessive number ofcoordinate conversions, making the process overly difficult andinaccurate.

[0397] To minimize navigational and display overhead, a Cartesian X,Y,Zcoordinate system is used for the navigation computations, map databaseand display presentations. Many X,Y,Z map database formats are in usetoday, but many are generated as a 2-D projection with altitude measuredabove mean sea level. Two examples of this type of system are UniversalTransverse Mercator (UTM) and State Plane Coordinate System (SPCS).Neither one of these systems is continuous around the world, each sufferfrom discontinuities and scale deformity. Furthermore, neither of thesesystems is directly compatible with GPS and also requires coordinateconversions. If the map, travel path waypoints, navigational processing,navigational screen graphics and airport control and managementfunctions are in the Cartesian coordinate frame, the overall processingis greatly simplified.

[0398] In the graphical navigation display FIG. 18 , the perspective isthat of a pilot from behind his current GPS position 84 . From thisvantage point 85, the pilot can view his current position 84 and hisplanned travel path 86 . As the aircraft moves, its precise ECEF X,Y,Zvelocity 87 components are used to determine how far back 88 and in whatdirection the observation is conducted from. This is determined bytaking the current ECEF velocity 87, negating it and multiplying it by aprogrammable time value (step-back time). When applied to the aircraft'scurrent position 84, this results in an observation point 89 which isalways looking at the current position 84 and ahead in the direction oftravel 87.

[0399] Once the observation point 89 is established in the 3-D Cartesiancoordinate system, an imaginary mathematical focal plane 90 isestablished containing the current position 84. The focal plane 90 isorthogonal to the GPS-derived CEF velocity vector 87. The mathematicalfocal plane 90 represents the imaginary surface where the navigationinsert 91 will be presented. The focal plane is always, by definition,orthogonal to the viewing point 85. The travel path 86 composed of ECEFX,Y,Z waypoints (92-95) is drawn into the 3-dimensional map. The pointon the true travel path 86 which is perpendicular to the currentposition 84 represents the center 96 of the navigational insert screen91. The orientation of the navigational insert with respect to thehorizontal axis is determined by the roll of the aircraft. The roll maybe determined through the use of multiple GPS antennas located at knownpoints on the aircraft or may be determined by inertial sensors and thenconverted to the ECEF coordinate frame. Vector mathematics performed inthe ECEF coordinate frame are then used to determine the new rotatedcoordinates of the navigation screen insert 91. The rotated coordinatesare then translated through the use of the graphical translation matrixand drawn into the 3-D map 97.

[0400] The final step is the placement of the current position‘cross-hair’ symbol 84 with respect to travel path 86. The aircraft'sGPS position, previous and next waypoints are used to determine the ECEFcross track vector 98. The cross track vector 98 is then broken downinto its local vertical 99 and local lateral 100 (horizontal)components. (Local components must be used here since the vertical andlateral vectors change as a function of location on the earth.) Thecross-hair symbol 101 is then drawn on to the focal (image) plane 90surface at the proper offset from the true course position indicated bythe center of the navigation screen insert 96. Thus, this displayprovides precise navigation information (lateral and vertical distanceto true course) with respect to true course, provides information on 3-Dairport features and shows the planned 3-D travel path. The element oftime may also be presented in this display format as an arrow (drawn inthe direction of travel) of variable length where the length indicatesspeed up or slow down information.

[0401] The construction of this type of display in other than ECEFcoordinates entails substantial coordinate conversion and additionalprocessing. Again, for simplicity and compatibility with proven3-dimensional graphic techniques, an ECEF Cartesian X,Y,Z coordinateframework is desired.

[0402] GPS NAVIGATOR DISPLAY

[0403] Various display formats are used to provide the GPS navigationalinformation to the pilot. The area navigation display shown in FIG. 19features auto-scaling range 102 rings 103 which provide course, 104bearing 105 and range distance to the waypoint. The length of the course104 and bearing lines 105 superimposed on the ring scale 103 areproportional to the distance from the waypoint. The compass orientationof the bearing line 105 provide the course to travel from the currentposition to the waypoint. The course line 104 indicates the compassdirection of current travel. The display also provides altitudeinformation as a auto-scaling bar chart display 106 with indicated go upor down information.

[0404] In this manner the area navigation display provides thefollowing:

[0405] 1. Range to the waypoint based on length of the line and anautoranging scale

[0406] 2. Compass heading to travel to the waypoint

[0407] 3. Compass heading of current travel

[0408] 4. Autoranging altitude navigation bar graph display

[0409] The GPS landing display is shown in FIG. 20. This display isactivated when the first GPS waypoint at the top of the glide slope isreached. The precision landing display is composed of a simple heavycross 107 which moved about on an X Y graticuled cross hair display 108.Textual TURN LEFT/TURN RIGHT and GO UP/GO DOWN messages are presented tothe pilot when the aircraft is more than a predetermined amount eg. 10.0meters off of true course.

[0410] Another display format utilizing a 3-D map is provided in FIG.21. This display technique provides a 3-D view of the approachingairport as viewed from the aircraft's position. The techniques describedabove for the cross hair navigation screen are identical to those usedin the 3-D approach presentation. In the 3-D approach presentation, aconical zone 109 is constructed around the line 110 between the landingapproach waypoints. The apex of the cone is at the touch down point 111and the base of the cone is at the top of the glide slope waypoint. This3-D object is viewed normal to the line between the current and previouswaypoint as shown in FIG. 21.

[0411] The cone is sliced at the point on the line (formed by thecurrent and previous waypoint) perpendicular to the present position112. The resulting cross section then effectively represents the crosshair symbology implemented in the graphical GPS landing display. Thecurrent position is then displayed within the conical cross section 113of the glide slope zone 109. A position not in the center of the displaymeans the aircraft is not on true course. For example, a position reportin the upper right of the display cross section means the aircraft istoo high and too far to the right. In this case the pilot should turnleft and go down. As the aircraft gets closer to the touch down point,the conical cross section scale gets smaller. Once the touchdownwaypoint 114 is reached, the display reverts to a plan view of theairport similar to that shown in FIG. 8 which is then used for surfacenavigation. The graphical nature if this display format is useful in theair and on the ground, but requires very fast graphical andcomputational performance. The advantage of this system is that itminimizes many of the navigational calculations such as cross trackerrors, but requires moderate spatial graphical computations and fastdisplay performance.

[0412] Waypoint Database Definition Software Example

[0413] AC&M SUBSYSTEMS

Communications Processor and Communication Flow

[0414] The processing of data communications within the airport is a keyelement of any GPS-based airport control and management system. Aminimum of three types of messages must be addressed:

[0415] (1) the broadcast of Differential GPS correction messages to thevehicles

[0416] (2) the transmission and receipt of Automatic DependentSurveillance (ADS) messages (3) the transmission of control messagesfrom the AC&M to the vehicle and vice versa.

[0417] A high level block diagram of the Airport Communications Systemand its interfaces to other major elements of the AC&M subsystem isprovided in FIG. 22.

[0418] In this design, all ADS and A/V messages are received by the AC&MProcessor 115 and are forwarded to the COMM Processor 116 forretransmission to the vehicles. The AC&M Processor is also used tocompose ATC messages which are also forwarded to the vehicles throughthe COMM interface or passed to the local Graphics Processor 117 tocontrol the situation display presentation. The COMM processor 116 alsotransmits the differential correction messages generated by thereference station 118 directly to the vehicles.

Differential GPS Overview

[0419] Real time differential correction techniques compensate for anumber of error sources inherent to GPS. The idea is simple in conceptand basically incorporates two or more GPS receivers, one acting as astationary base station 118 and the other(s) acting as rovingreceiver(s) 119, 120. The differential base station is “anchored” at aknown point on the earth's surface. The base station receives thesatellite signals, determines the errors in the signals and thencalculates corrections to remove the errors. The corrections are thenbroadcast to the roving receivers.

[0420] Real time differential processing provides accuracy of 10.0meters or better (typically 1.0-5.0 meters for local differentialcorrections). The corrections broadcast by the base station are accurateover an area of about 1500 km or more. Typical positional degradation isapproximately a few millimeters of position error per kilometer of basestation and roving receiver separation.

[0421] Through the implementation of local differential GPS techniques,SA errors are reduced significantly while the atmospheric errors arealmost completely removed. Ephemeris and clock errors are virtuallyremoved as well.

Antenna Placement

[0422] A site survey of potential differential base station sites shouldbe performed to determine a suitable location for the GPS antenna. Thelocation should have a clear view of the sky and should not be locatednear potentially reflective surfaces (within about 300 meters). Theantenna site should be away from potentially interfering radiationsources such as radio, television, radar and communicationstransmitters. After a suitable site is determined, a GPS survey shouldbe conducted to determine the precise location of the GPSantenna—preferably to centimeter level accuracy. This should beperformed using survey grade GPS equipment.

[0423] Survey grade GPS equipment makes use of the 19 and 21 centimeterwavelength of the L1 and L2 GPS transmissions. Real time kinematic orpost processing GPS surveys may be conducted. Real time kinematicutilizes a base station located at a precise location which broadcastscarrier phase correction and processing data to a radio receiver andprocessing computer. Code, carrier integral cycles and carrier phaseinformation are used at the survey site to calculate the WGS 84 antennaposition. In the post processing survey mode, subframe information,time, code, carrier, and carrier phase data are collected for a periodof time. This data is later post processed using precise ephemerideswhich are available from a network of international GPS sites. Thecollected information is then post processed with post-fit preciseorbital information.

Base Station Operational Elements

[0424] The precisely surveyed location of the GPS antenna is programmedinto the reference station as part of its initial installation and setup procedures. Industry standard reference stations determine pseudorange and delta range based on carrier smoothed measurements for allsatellites in view. Since the exact ECEF position of the antenna isknown, corrections may be generated for the pseudo range and delta rangemeasurements and precise time can be calculated.

[0425] Naturally occurring errors are, for the most part, slow changingand monotonic over the typical periods of concern. When SA is notinvoked, delta range corrections provide a valid method of improvingpositional accuracy at the roving receivers using less frequentcorrection broadcasts. With the advent of SA and its random, quickchanging non-monotonic characteristics, delta range corrections becomesomewhat meaningless and may actually degrade the system performanceunder some conditions.

[0426] As shown previously in FIG. 22 the DGPS correction messages arebroadcast by the reference station and received by the roving receivers.The corrections are applied directly to the differential GPS receiver.The DGPS receiver calculates the pseudo range and the delta rangemeasurements for each satellite in the usual manner. Prior to performingthe navigation solution, the received pseudo range and delta rangecorrections are applied to the internal measurements. The receiver thencalculates corrected position, velocity and time data.

[0427] Since differential GPS eliminates most GPS errors, it providessignificant improvements in system reliability for life critical airportoperations. Short term and long term drift of the satellite orbits,clocks and naturally occurring phenomenon are compensated for bydifferential GPS as are other potential GPS satellite failures.Differential GPS is mandatory in the airport environment from areliability, accuracy and fault compensating perspective.

[0428] As with autonomous GPS receiver operation, multipath is apotential problem. The differential reference station cannot correct formultipath errors at the roving receiver(s). Antenna design and placementconsiderations, and receiver design characteristics remain the bestsolutions to date in the minimization of multipath effects.

ADS Messages

[0429] ADS messages are generated on board each vehicle and broadcast tothe AC&M System. The message format is shown below:

MSG HEADER, VEHICLE ID, VEHICLE TYPE, ECEF X, ECEF Y, ECEF Z,

ECEF X VEL, ECEF Y VEL, ECEF Z VEL <CR><LF>

[0430] On board each vehicle, the GPS-based position and velocity datais converted to Earth Centered Earth Fixed (ECEF) coordinates for use inthe navigation and zone processing algorithms if necessary. Forsimplicity, this format moused in the ADS transmission as well. Uponreceipt of an ADS message, the AC&M Processor 115 forwards the messageto the COMM Processor 116 then stores the data in the vehicle database.The stored ECEF position and velocity data is used to perform collisionprediction, zone incursion, lighting control and navigation processingat the AC&M station.

ATC Messages

[0431] Air Traffic Control (ATC) messages are composed using the AC&Mstation. The ATC messages are used locally to control the AC&M graphicsdisplay 117 or present current status information to the user. ATCmessage are also broadcast to the vehicles 119 and 120 through the COMMProcessor 116. All ATC messages utilize an explicit acknowledgmentmessage. If an acknowledgment is not received within a defined timeinterval, the message is automatically retransmitted. The standardformat is shown below.

$ATC, MESSAGE TYPE, VEHICLE ID, MESSAGE DATA <CR><LF>.

Error Detection and Correction

[0432] In the demonstration prototype system, Cyclical RedundancyChecking (CRC) is performed on all messages, with the exception of the[RTCM-104] differential correction messages generated in the BaseStation 118. In this scheme, ADS messages are discarded if an error isdetected in the received message. This has not been a significantproblem for the prototype system since the next message is received inone (1.0) second. The ATC messages directed to specific vehicles alsosupport CRC error detection. ATC messages are “addressed” to a specificA/V and expect an explicit acknowledgment. Upon receipt of an ATCmessage, the ANV sends back a valid “message received” acknowledgment.The ATC message is discarded by the A/V if an error is detected. In thiscase, no message received acknowledgment is generated. If no “messagereceived” acknowledgment is received by the AC&M 115 within a presettime interval, the original message is immediately retransmitted. ATCmessages require a corresponding acknowledgment since they may representcritical controller instructions and airport and safety operations couldbe compromised if the message fails to reach its destination.

[0433] The CRC system operated effectively in the demonstrationprototype system, but a more robust communication error detection andcorrection capability may be required for end state deployment. Forwarderror correction and Vterbi—Trellis techniques provide a cost effectiveforward error correction capability. These techniques are widely used incommercial modem technology and are available in Application SpecificIntegrated Circuits (ASIC). Wide spread use of the technology makes itvery cost effective for use in future airport communication systems.

[0434] AC&M PROCESSOR AND AC&M PROCESSING FLOW

[0435] A block diagram of the AC&M Processor is provided in FIG. 23.

[0436] The AC&M Processor 121 is based on a 33 MHz 386 processor with a387 math co-processor. This processor performs the following functions:

[0437] Interfaces to communication digital datalinks

[0438] Receives ADS vehicle broadcasts

[0439] Receives acknowledgment messages from vehicles

[0440] Generates and transmits messages to vehicles

[0441] Performs collision prediction processing for each vehicle

[0442] Monitors zone and runway incursion conditions

[0443] Controls runway intersections and runway clearance lights

[0444] Maintains and controls vehicle, waypoint and zone databases

[0445] Performs navigational processing for on-off course checking

[0446] Performs map layer control and assignment

[0447] Sends vehicle reports and commands to Graphic Processor forsituation display

[0448] Provides a touch screen and keyboard command interface

[0449] Representative command functions are described in the followingsection.

Touch Screen

[0450] The AC&M touch screen provides an efficient means of commandinput for interfacing to the airport management system. The touch screenis used to perform the following high level functions:

[0451] Command interface to the Graphics Processor

[0452] Command interface to the AC&M Processor

[0453] Communication interface to properly equipped vehicles andaircraft

[0454] Display of various AC&M data lists

[0455] Display of vehicle status information

[0456] The touch screen is organized into four discrete displayareas—the Command List, the Message Composition and Response (MC&R)Window, the Alerts Window, and the Vehicle List. The following figureshows the touch screen layout used during the final demonstration. FIG.34 depicts the touch screen with representative information.

[0457] The Command List, as shown on the right in the figure below, isused to provide key high level command functions. When a command isinvoked, it is emphasized in the Command List and remains emphasizeduntil the command is canceled or completed.

[0458] After command selection, the valid command options are displayedin the large MC&R window to the left. The MC&R window has two majorfunctions—it is used to compose ATC messages and it is used to displayinformation to the operator. During message composition, the MC&R windowis used to prompt the operator and provide a series of options relatingto the content and destination of the message. The MC&R window alsoserves as the display presentation medium for list displays such as theVehicle Data display.

[0459] Critical watch and warning messages are presented to the operatorin the Alerts window of the touch screen. The Alerts window displaysmessages generated as a result of a potential collision condition, zoneincursion or off course determination.

[0460] The Vehicle List provides the operator with a list of the activevehicles. Vehicles may be selected from the list during the messagecomposition activities.

[0461] Numerous commands have been implemented to demonstrate thecapability of the touch screen data entry device. Representative commandfunctions are described in the following section.

AC&M Command List Touch Screen

[0462] The AC&M touch screen provides an efficient means of commandinput for interfacing to the airport management system. The touch screenis used to perform the following high level functions:

[0463] Command interface to the Graphics Processor

[0464] Command interface to the AC&M Processor

[0465] Communication interface to properly equipped vehicles andaircraft

[0466] Display of various AC&M data lists

[0467] Display of vehicle status information

[0468] The touch screen is organized into four discrete displayareas—the Command List, the Message Composition and Response (MC&R)Window, the Alerts Window, and the Vehicle List. The following figureshows the touch screen layout used during the final demonstration. FIG.34 depicts the touch screen with representative information.

[0469] The Command List, as shown on the right in the figure below, isused to provide key high level command functions. When a command isinvoked, it is emphasized in the Command List and remains emphasizeduntil the command is canceled or completed.

[0470] After command selection, the valid command options are displayedin the large MC&R window to the left. The MC&R window has two majorfunctions—it is used to compose ATC messages and it is used to displayinformation to the operator. During message composition, the MC&R windowis used to prompt the operator and provide a series of options relatingto the content and destination of the message. The MC&R window alsoserves as the display presentation medium for list displays such as theVehicle Data display.

[0471] Critical watch and warning messages are presented to the operatorin the Alerts window of the touch screen. The Alerts window displaysmessages generated as a result of a potential collision condition, zoneincursion or off course determination.

[0472] The Vehicle List provides the operator with a list of the activevehicles. Vehicles may be selected from the list during the messagecomposition activities.

[0473] Numerous commands have been implemented to demonstrate thecapability of the touch screen data entry device. Representative commandfunctions are described in the following section.

AC&M Command List

[0474] ARRIVAL WAYPOINTS

[0475] The ARRIVAL WAYPOINTS command is issued to grant a landingclearance to an approaching aircraft and provide it with a set ofwaypoints for the landing operation. The command is invoked by touchingthe ARRIVAL WAYPOINT soft function key on the AC&M touch screen.

[0476] Upon invocation, the following steps are followed:

[0477] 1. The ARRIVAL WAYPOINTS soft function key is highlighted.

[0478] 2. The list of valid vehicle ids is displayed in the VEHICLE LISTwindow. The user is prompted to select one of the vehicles.

[0479] 3. Upon selection of a valid vehicle, a description of eachpredefined arrival waypoint path is displayed in the MESSAGE COMPOSITIONAND RESPONSE (MC&R) window. The user is prompted to select one of thewaypoint lists.

[0480] 4. Upon selection of the waypoint list, the correspondingwaypoints are drawn into the AC&M's digital map display. The user isthen prompted as to whether the waypoints are correct.

[0481] 5. If the user accepts the waypoints, an ATC message is composedand transmitted to the vehicle. The waypoints are automatically loadedinto the AC&M's mirrored navigator. The MC&R window is cleared and amessage completed indicator is displayed.

[0482] 6. If the user does not accept the waypoints, the waypoints drawninto the map display are cleared, the MC&R window is cleared and nowaypoints are processed.

[0483] DEPARTURE WAYPOINTS

[0484] The DEPARTURE WAYPOINTS command is issued to grant a takeoffclearance to a departing aircraft and provide it with a set of waypointsfor the operation. The command is invoked by touching the DEPARTUREWAYPOINT soft function key on the AC&M touch screen.

[0485] Upon invocation, the following steps are followed:

[0486] 1. The DEPARTURE WAYPOINTS soft function key is highlighted.

[0487] 2. The list of valid vehicle ids is displayed in the VEHICLE LISTwindow. The user is prompted to select one of the vehicles.

[0488] 3. Upon selection of a valid vehicle, a description of eachpredefined departure waypoint path is displayed in the MESSAGECOMPOSITION AND RESPONSE (MC&R) window. The user is prompted to selectone of the waypoint lists.

[0489] 4. Upon selection of the waypoint list, the correspondingwaypoints are drawn into the AC&M's digital map display. The user isthen prompted as to whether the waypoints are correct.

[0490] 5. If the user accepts the waypoints, an ATC message is composedand transmitted to the vehicle. The waypoints are automatically loadedinto the AC&M's mirrored navigator. The MC&R window is cleared and amessage completed indicator is displayed.

[0491] 6. If the user does not accept the waypoints, the waypoints drawninto the map display are cleared, the MC&R window is cleared and nowaypoints are processed.

[0492] SURFACE WAYPOINTS

[0493] The SURFACE WAYPOINTS command is issued to grant a groundclearance to an aircraft or surface vehicle and provide it with a set ofwaypoints for the operation. The command is invoked by touching theSURFACE WAYPOINT soft function key on the AC&M touch screen.

[0494] Upon invocation, the following steps are followed:

[0495] 1. The SURFACE WAYPOINTS soft function key is highlighted.

[0496] 2. The list of valid vehicle ids is displayed in the VEHICLE LISTwindow. The user is prompted to select one of the vehicles.

[0497] 3. Upon selection of a valid vehicle, a description of eachpredefined surface waypoint path is displayed in the MESSAGE COMPOSITIONAND RESPONSE (MC&R) window. The user is prompted to select one of thewaypoint lists.

[0498] 4. Upon selection of the waypoint list, the correspondingwaypoints are drawn into the AC&M's digital map display. The user isthen prompted as to whether the waypoints are correct.

[0499] 5. If the user accepts the waypoints, an ATC message is composedand transmitted to the vehicle. The waypoints are automatically loadedinto the AC&M's mirrored navigator. The MC&R window is cleared and amessage completed indicator is displayed.

[0500] 6. If the user does not accept the waypoints, the waypoints drawninto the map display are cleared, the MC&R window is cleared and nowaypoints are processed.

[0501] CLEAR PATH WAYPOINTS

[0502] The CLEAR PATH WAYPOINTS command is issued to manually end apreviously granted clearance and clear any pending waypoints for aspecific vehicle. The command is invoked by touching the CLEAR PATHWAYPOINTS soft function key on the AC&M touch screen.

[0503] Upon invocation, the following steps are followed:

[0504] 1. The CLEAR PATH WAYPOINTS soft function key is highlighted.

[0505] 2. The list of valid vehicle ids is displayed in the VEHICLE LISTwindow. The user is prompted to select one of the vehicles.

[0506] 3. Upon selection of a valid vehicle, a clear waypoints commandis issued to the vehicle, clearing its remaining waypoints. Similarly,the clearance status and waypoints at the AC&M system are cleared aswell.

[0507] AIRPORT LIGHTS

[0508] The AIRPORT LIGHTS command is issued to manually change thestatus of a specific set of runway approach, departure or intersectionlights. The command is invoked by touching the AIRPORT LIGHTS softfunction key on the AC&M touch screen.

[0509] Upon invocation, the following steps are followed:

[0510] 1. The AIRPORT LIGHTS soft function key is highlighted.

[0511] 2. Each lighting system and its current status (ON or OFF) isdisplayed in the MC&R window. The user is prompted to select the desiredlight(s) from the window.

[0512] 3. Upon selection of a set of lights, the status is toggled andthe corresponding lights on the map lighting board are changedaccordingly.

[0513] VEHICLE FILTER

[0514] The VEHICLE FILTER command is issued to enable or suppress thedisplay of a particular type of vehicle by altering the status of itsgraphic layer. The command is invoked by touching the VEHICLE FILTERsoft function key on the AC&M touch screen.

[0515] Upon invocation, the following steps are followed:

[0516] 1. The VEHICLE FILTER soft function key is highlighted.

[0517] 2. The current vehicle types are displayed in the MC&R windowwith the current filter status (ON or OFF) as shown: LIMITED ACCESS AREAGROUND VEHICLE ON EMERGENCY/SERVICE GROUND VEHICLE ON ARRIVAL AIRCRAFTON DEPARTURE AIRCRAFT ON ALL VEHICLES ON

[0518] 3. The user has the capability to suppress and re-enable variousvehicle types by selecting it from the MC&R window.

[0519] 4. Upon selection, the user is prompted to accept the command. Ifthe command is selected, the vehicle type's status is toggled and thevehicle is either suppressed from the map display or redisplayed ifpreviously suppressed.

[0520] Vehicle types which are suppressed are not displayed on the AC&Mgraphics display unless they are in a collision or zone incursioncondition.

[0521] 5. If NO is selected, the vehicle type's status remainsunchanged.

[0522] LAYER FILTER

[0523] The LAYER FILTER command is issued to manually change the statusof a specific graphic layer. Layers which are masked are no longerdisplayed. The command is invoked by touching the LAYER FILTER softfunction key on the AC&M touch screen.

[0524] Upon invocation, the following steps are followed:

[0525] 1. The LAYER FILTER soft function key is highlighted.

[0526] 2. The current LAYER types are displayed in the MC&R window withthe current filter status (ON or OFF) as shown below: LAYER TYPE STATUSRANGE RINGS ON RANGE RINGS, 5 MILE INCREMENTS ON AIRPORT LIGHTINGSYSTEMS (RNWY 35) OFF AIRPORT LIGHTING SYSTEMS (RNWY 24) OFF TRACKEDSURFACE VEHICLES (LIMITED ACCESS) ON TRACKED SURFACE VEHICLES (FULLACCESS) ON TRACKED DEPARTURE AIRCRAFT ON TRACKED ARRIVAL AIRCRAFT ONARRIVAL WAYPOINTS OFF DEPARTURE WAYPOINTS OFF SURFACE WAYPOINTS OFFCUSTOM WAYPOINTS DEFINITION OFF AIRPORT SURFACE ZONES OFF WEIGHT LIMITEDZONES OFF RESTRICTED TRAVEL AREA OFF AIRSPACE HAZARD ZONES OFF OPENCONSTRUCTION ZONES OFF CLOSED CONSTRUCTIONS ZONES OFF

[0527] 3. The user has the capability to suppress and re-enable variouslayers by selecting it from the MC&R window.

[0528] 4. Upon selection, the user is prompted to accept the command. Ifthe command is selected, the layer's status is toggled and the layer iseither suppressed from the map display or re&splayed if previouslysuppressed.

[0529] Vehicle types which are suppressed are not displayed on the AC&Mgraphics display unless they are in a collision or zone incursioncondition. Special category, watch or warning layers are neversuppressed.

[0530] 5. If NO is selected, the layer's status remains unchanged.

[0531] VEHICLE DATA

[0532] The VEHICLE DATA command is issued to display status informationfor a particular vehicle. The vehicle data is displayed in the MC&Rwindow. The command is invoked by touching the VEHICLE DATA softfunction key on the AC&M touch screen.

[0533] Upon invocation, the following steps are followed:

[0534] 1. The VEHICLE DATA soft function key is highlighted.

[0535] 2. The list of valid vehicle ids is displayed in the VEHICLE LISTwindow. The user is prompted to select one of the vehicles.

[0536] 3. Upon selection of a valid vehicle, data corresponding to thatvehicle is displayed in the MC&R window. The data is updatedautomatically as the vehicle's ADS messages are received at the AC&M.The data includes the vehicle id, tag, type, minimum safe distance forcollision processing, heading and speed. If the vehicle has beenassigned waypoints the current waypoint, 3-D range and cross track errorare also displayed. The vehicle data remains displayed until anothersoft function key is invoked.

[0537] DISPLAY VIEW

[0538] The DISPLAY VIEW command is issued to change the display viewpresented on the situation display. The command is invoked by touchingthe DISPLAY VIEW soft function key on the AC&M touch screen.

[0539] Upon invocation, the following steps are followed:

[0540] 1. The DISPLAY VIEW soft function key is highlighted.

[0541] 2. Upon invocation, the following display view options aredisplayed in the MC&R window: VIEW ID DESCRIPTION 00 PLAN VIEW 10 MILERANGE 01 PLAN VIEW 5 MILE RANGE 02 PLAN VIEW 1 MILE RANGE 03 PLAN VIEW.5 MILE RANGE 04 RUNWAY 35 05 RUNWAY 17 06 RUNWAY 24 07 RUNWAY 06 08GATE AREA 09 FIRE, CRASH AND RESCUE 10 TERMINAL BUILDING 11 3D VIEWRUNWAY 35 12 3D VIEW RUNWAY 17 13 3D VIEW RUNWAY 24 14 3D VIEW RUNWAY 0615 APPROACH VIEW RUNWAY 35 16 APPROACH VIEW RUNWAY 17 17 APPROACH VIEWRUNWAY 24 18 APPROACH VIEW RUNWAY 06

[0542] 3. Upon selection of the desired view, the AC&M map display isredrawn.

[0543] AIRPORT LIGHTS: The system also demonstrates the capability tocontrol airport lights based on GPS inputs and current clearance status.

[0544] RUNWAY 35 LIGHT STATUS RUNWAY 35 LIGHT STATUS ACTIVITY LANDINGINTERSECTION TAKEOFF DESCRIPTION LIGHTS LIGHTS LIGHTS NO ACTIVITY STATE(RUNWAY 35) RED OFF RED (RUNWAY 17) RED OFF RED TAKE OFF CLEARANCEGIVEN - 35 (35 -TAKEOFF RED OFF RED END) (17 - OPPOSITE RED OFF RED END)AIRCRAFT ENTERS RNWY 35 ZONE (35 - TAKEOFF RED RED GREEN END) (17 -OPPOSITE RED RED RED END) TAKE OFF COMPLETED (35 - TAKEOFF RED OFF REDEND) (17 - OPPOSITE RED OFF RED END) LANDING CLEARANCE ISSUED - 35 (35 -APPROACH GREEN RED RED END) (17 - OPPOSITE RED RED RED END) ARRIVALAIRCRAFT EXITS RUNWAY (RUNWAY 35) RED OFF RED (RUNWAY 17) RED OFF REDRUNWAY INCURSION OCCURRED (RUNWAY 35) FLASH FLASH FLASH RED/GREENRED/OFF RED/GREEN (RUNWAY 17) FLASH FLASH FLASH RED/GREEN RED/OFFRED/GREEN RUNWAY INCURSION ENDS (RUNWAY 35) RED OFF RED (RUNWAY 17) REDOFF RED

[0545] Airport lighting control techniques are provided as ademonstration mechanism and are not intended to dictate a specificlighting scheme for airports.

Situation Display

[0546] A vehicle database is maintained by the AC&M and on board ‘fullyequipped’ vehicles to provide a situational awareness capability to thecontroller and/or vehicle operator. GPS-based situational awarenessrequires the integration of a datalink between the aircraft, surfacevehicles and AC&M system. In the demonstration prototype system, theposition and velocity information determined on board each vehicle isbroadcast over an experimental VHF datalink and received by the AC&M. Atthe AC&M, the message is assembled into a dynamic vehicle database. Aseach ADS message is received, the following fields in the vehicledatabase are updated:

[0547] Vehicle I

[0548] Vehicle Type

[0549] Position (ECEF X,Y,Z)

[0550] Velocity (ECEF X,Y,Z)

[0551] In order to present the vehicle position data graphically, thefollowing information is also maintained in the vehicle database:

[0552] Layer ID

[0553] Vehicle Color

[0554] Each vehicle is assigned a map layer based on vehicle type. Thedigital airport map features numerous object oriented layers which areused to segregate various types of graphical information. By assigningvehicles to specific map layers, spatial filtering may be performed on alayer by layer basis. Color may be assigned by layer or by individualvehicle.

[0555] Position reporting functions operating on a moving platformpotentially suffer from a positional error introduced by processingtime. To compensate for this factor, the precise DGPS derived ECEFvelocity components are used to project the position ahead. As each ADSmessage is received, a latency compensation time projection factor isapplied in an ECEF Velocity x Time relationship. The new, projected ECEFposition is then considered the current position, is stored in thevehicle database and is used throughout the navigation and collisionprediction algorithms.

[0556] Once the dynamic vehicle database is constructed, a sequentialscanning of the database is performed as new ADS position reports arereceived. Vehicles outside of the defined range are filtered out.Vehicles within range are displayed in the 3-D airport map. In thismanner, graphical situational awareness is provided at the AC&M and onboard the vehicles/aircraft.

Collision Prediction Processing

[0557] As ADS messages are received, collision prediction processing isperformed using the current GPS data and the information stored in thevehicle database. The following database fields are used in thecollision prediction processing: Collision Time Time (secs) when acollision may occur Collision Count Number of potential collisionsdetected Collision Condition Warning or watch state detected CollisionSeparation Current collision separation Radius Vehicle's minimumseparation radius

[0558] A ‘rough check’ is performed to determine if there are anyvehicles in the immediate vicinity of the current vehicle. The currentvehicle's position is projected ahead using a definedMAXIMUM_PROJECTION_FACTOR. The vehicle database is sequentially scanned.The position of the first vehicle in the database is projected ahead inthe same manner. If the projected positions intersect, further collisionchecking is performed.

[0559] When further collision checking is warranted, the currentvehicle's position is projected ahead by incrementing time in one secondintervals. At each interval, an imaginary sphere is drawn around thevehicle using a predefined radius based on the vehicle's minimum safeseparation. Similarly, the position of the next vehicle in the databaseis projected ahead. If the two imaginary spheres intersect and the timeinterval of the intersection is less than or equal to theMINIMUM_WARNING_TIME factor, a collision warning condition is generated.If the two imaginary spheres intersect at a time interval greater thanthe MINIMUM_WARNING_TIME but less than the MINIMUM_WATCH_TIME, acollision watch condition is generated.

[0560] If a collision watch condition is generated, the vehicles in thewatch condition are displayed in YELLOW on the AC&M map display. Awarning message is displayed to the operator in the Alerts window of thetouchscreen. If a warning condition is detected, the vehicle's symbol isdisplayed in RED on the graphics screen and a warning message isdisplayed in the Alert window.

[0561] During any collision condition, the vehicle's symbol is moved toa dedicated watch or warning map layer. These layers are reserved forcritical operations and cannot be suppressed by the user.

[0562] The following collision data was generated from actual collisiontests and represents two surface vehicles driving towards each other.During this test scenario, the following factors were used:MINIMUM_WARNING_TIME 3 seconds MINIMUM_WATCH_TIME 7 seconds RADIUS,VEHICLE 03 7 meters RADIUS, VEHICLE 04 7 meters

[0563] Note that a COLLISION WATCH is detected when the distance betweenthe two vehicles is less than the sum of its radii. A COLLISION WARNINGis detected when the intersection occurs within the MINIMUM_WARNING_TIMEof 3 seconds or less. Also note that as soon as the vehicles pass oneanother and the distance between them begins to increase, no WATCH orWARNING condition is detected.

[0564] VEH=03 DIST=74.9 PROJ TIME=1 SECONDS

[0565] VEH=03 DIST=64.7 PROJ TIME=2 SECONDS

[0566] VEH=03 DIST=54.5 PROJ TIME=3 SECONDS

[0567] VEH=03 DIST=44.3 PROJ TIME=4 SECONDS

[0568] VEH=03 DIST=34.2 PROJ TIME=5 SECONDS

[0569] VEH=03 DIST=24.0 PROJ TIME=6 SECONDS

[0570] VEH=03 DIST=14.0 PROJ TIME=7 SECONDS COLLISION WATCH

[0571] VEH=04 DIST=70.0 PROJ TIME=1 SECONDS

[0572] VEH=04 DIST=59.7 PROJ TIME=2 SECONDS

[0573] VEH=04 DIST=49.5 PROJ TIME=3 SECONDS

[0574] VEH=04 DIST=39.2 PROJ TIME=4 SECONDS

[0575] VEH=04 DIST=29.0 PROJ TIME=5 SECONDS

[0576] VEH=04 DIST=18.8 PROJ TIME=6 SECONDS

[0577] VEH=04 DIST=8.9 PROJ TIME=7 SECONDS COLLISION WATCH

[0578] VEH=03 DIST=64.1 PROJ TIME=1 SECONDS

[0579] VEH=03 DIST=53.7 PROJ TIME=2 SECONDS

[0580] VEH=03 DIST=43.4 PROJ TIME=3 SECONDS

[0581] VEH=03 DIST=33.1 PROJ TIME=4 SECONDS

[0582] VEH=03 DIST=22.8 PROJ TIME=5 SECONDS

[0583] VEH=03 DIST=12.7 PROJ TIME=6 SECONDS COLLISION WATCH

[0584] VEH=04 DIST=59.1 PROJ TIME=1 SECONDS

[0585] VEH=04 DIST=48.6 PROJ TIME=2 SECONDS

[0586] VEH=04 DIST=38.1 PROJ TIME=3 SECONDS

[0587] VEH=04 DIST=27.6 PROJ TIME=4 SECONDS

[0588] VEH=04 DIST=17.1 PROJ TIME=5 SECONDS

[0589] VEH=04 DIST=7.0 PROJ TIME=6 SECONDS COLLISION WATCH

[0590] VEH=03 DIST=53.3 PROJ TIME=1 SECONDS

[0591] VEH=03 DIST=42.7 PROJ TIME=2 SECONDS

[0592] VEH=03 DIST=32.3 PROJ TIME=3 SECONDS

[0593] VEH=03 DIST=21.8 PROJ TIME=4 SECONDS

[0594] VEH=03 DIST=11.4 PROJ TIME=5 SECONDS COLLISION WATCH

[0595] VEH=04 DIST=47.8 PROJ TIME=1 SECONDS

[0596] VEH=04 DIST=37.1 PROJ TIME=2 SECONDS

[0597] VEH=04 DIST=26.4 PROJ TIME=3 SECONDS

[0598] VEH=04 DIST=15.8 PROJ TIME=4 SECONDS

[0599] VEH=04 DIST=5.4 PROJ TIME=5 SECONDS COLLISION WATCH

[0600] VEH=03 DIST=41.9 PROJ TIME=1 SECONDS

[0601] VEH=03 DIST=31.2 PROJ TIME=2 SECONDS

[0602] VEH=03 DIST=20.5 PROJ TIME=3 SECONDS

[0603] EH=03 DIST=9.9 PROJ TIME=4 SECONDS COLLISION WATCH

[0604] VEH=04 DIST=36.6 PROJ TIME=1 SECONDS

[0605] VEH=04 DIST=25.9 PROJ TIME=2 SECONDS

[0606] VEH=04 DIST=15.3 PROJ TIME=3 SECONDS

[0607] VEH=04 DIST=5.4 PROJ TIME=4 SECONDS COLLISION WATCH

[0608] VEH=03 DIST=31.9 PROJ TIME=1 SECONDS

[0609] VEH=03 DIST=21.2 PROJ TIME=2 SECONDS

[0610] VEH=03 DIST=10.6 PROJ TIME=3 SECONDS COLLISION WARNING

[0611] VEH=04 DIST=26.6 PROJ TIME=1 SECONDS

[0612] VEH=04 DIST=15.9 PROJ TIME=2 SECONDS

[0613] VEH=04 DIST=5.6 PROJ TIME=3 SECONDS COLLISION WARNING

[0614] VEH=03 DIST=14.4 PROJ TIME=1 SECONDS

[0615] VEH=03 DIST=4.6 PROJ TIME=2 SECONDS COLLISION WARNING

[0616] VEH=04 DIST=10.6 PROJ TIME=1 SECONDS COLLISION WARNING

[0617] VEH=03 DIST=5.9 PROJ TIME=1 SECONDS COLLISION WARNING

[0618] VEH=04 DIST=2.9 PROJ TIME=1 SECONDS COLLISION WARNING

[0619] DIST=5.4, VEHICLE SEPARATION IS INCREASING, STOP PROCESSING . . .

[0620] ZONE INCURSION PROCESSING

[0621] A 3-D map database and ECEF mathematical processing algorithmssupport the concept of zones. Zones are three dimensional shapes whichare used to provide spatial cueing for a number of constructs unique toDSDC's demonstration system. Zones may be defined around obstacles whichmay pose a hazard to navigation, such as transmission towers, tallbuildings, and terrain features. Zones may also be keyed to theairport's NOTAMS, identifying areas of the airport which have restrictedusage.

[0622] Zones are represented graphically on the map display andmathematically by DSDC's zone processing algorithms. Multi-sided zonesare stored in a zone database as a series of points. Each zone isassigned a zone id and type. The zone type is used to determine whethera particular zone is off-limits for a specific vehicle type.

[0623] Zone information is maintained in the zone database. A zoneincursion status field is also maintained for the vehicle in the vehicledatabase. If the vehicle is currently inside a zone, this field is usedto store the zone's id. If the vehicle is not inside a zone, this fieldis zero (0).

[0624] At the AC&M, zone incursion processing is performed in a mannersimilar to the collision processing described previously. As eachvehicle report is received, it is projected ahead by incrementing timeup to a MAX_ZONE_PROJECTION_FACTOR. At each interval, the vehicle'sprojected position is compared to each line of the zone as defined byits endpoints. If the vehicle's position is inside all of the linescomprising the zone and the current projection time is less than theMIN_ZONE_WARNING factor, a zone incursion warning is generated. If thevehicle's position is inside the zone and the current projection time isless than the MIN_ZONE_WATCH factor but greater than theMIN_ZONE_WARNING factor, a zone incursion watch is generated. As in thecollision processing, a zone incursion watch or warning will result in amessage displayed to the operator and a change in layer assignments forthe affected vehicle.

[0625] A zone incursion condition is automatically cleared when thevehicle exits the zone. All zones are defined as 3-dimensional entitiesand may be exited laterally or vertically. Heights may be assigned to‘surface’ zones individually or collectively. The concepts of3-dimensional zones is critical to an airport environment to preventpassing aircraft from triggering ground-based zones.

Runway Incursion Processing

[0626] If a zone incursion is detected, a further check is performed todetermine if the vehicle is entering or inside a runway zone. ForManchester Airport, five (5) runway zones have been defined:

[0627] RNWY_(—)35_ZONE

[0628] RNWY_(—)17_ZONE

[0629] RNWY_(—)24_ZONE

[0630] RNWY_(—)06_ZONE

[0631] RNWY_INT_ZONE “RUNWAY INTERSECTION VOLUME”

[0632] An additional field is maintained in the vehicle database toindicate whether a runway incursion state has been detected. As with thezone incursion field, the runway incursion value is set to the id of thezone (i.e., the runway) if an incursion is currently occurring and isset to zero (0) if there is no runway incursion.

[0633] If the vehicle is entering or inside a runway zone and is notcleared for that zone, a runway incursion condition is generated at theAC&M. As in any zone incursion situation, a watch or warning message isdisplayed in the AC&M Alerts window and the vehicle's symbol is moved tothe dedicated watch or warning map layer, changing its color to YELLOWor RED. In addition, the runway incursion results in a status change inthe runway's landing, takeoff and intersection lights forcing the lightsto flash on the affected (and related) runway(s). The following tabledescribes the lighting states for runway incursions in each of the fiverunway zones. RUNWAY INCURSION LIGHT STATES RNWY 35 RNWY 17 RNWY 24 RNWY06 ACTIVITY DESCRIPTION A D I A D I A D I A D I INCURSION - RNWY 35FLASH FLASH NO CHANGE NO CHANGE INCURSION ENDS DEFAULT DEFAULT NO CHANGENO CHANGE INCURSION - RNWY 17 FLASH FLASH NO CHANGE NO CHANGE INCURSIONENDS DEFAULT DEFAULT NO CHANGE NO CHANGE INCURSION - RNWY 24 NO CHANGENO CHANGE FLASH FLASH INCURSION ENDS NO CHANGE NO CHANGE DEFAULT DEFAULTINCURSION - RNWY 06 NO CHANGE NO CHANGE FLASH FLASH INCURSION ENDS NOCHANGE NO CHANGE DEFAULT DEFAULT INCUR. - INTERSECTION FLASH FLASH FLASHFLASH INCURSION ENDS DEFAULT DEFAULT DEFAULT DEFAULT

[0634] A runway incursion is automatically terminated when the incurringvehicle exits the runway. When the incursion condition is terminated,the lights on the affected runway return to their default state. As inall zone definitions, runway zones are 3-dimensional entities. Runwayzones are assigned a height of approximately 100 meters above thesurface of the runway in the prototype demonstration system. Therefor, arunway incursion occurs only when an uncleared vehicle enters the zoneat the surface level. Demonstration prototype lighting software isprovided below:

Lighting Control Software Example

[0635] /****************************************************************LIGHTS.H Description: lights.h contains the global constants and datastructures for the airport lights.****************************************************************/#define LIGHT_ADDR 0x300 /* address of digital IO board */ /*- light bitsettings, digital I/O card -*/ #define LANDING_35 0x01 #defineLANDING_17 0x02 #define LANDING_24 0x04 #define LANDING_06 0x08 #defineTAKEOFF_17 0x10 #define TAKEOFF_06 0x20 #define TAKEOFF_35 0x40 #defineTAKEOFF_24 0x80 /*----- light status states -----*/ #define NO_ACTIVITY0 #define RUNWAY_INCURSION 1 #define LANDING 2 #define TAKEOFF 3 #defineSURFACE 5 /*---- ruwnay id ----*/ #define RNWY_35 35 #define RNWY_17 17#define RNWY_24 24 #define RNWY_06 6 #define RNWY_INT 1/**************************************************************** FileName: LIGHTS.C Description: lights.c contains the procedures used updatethe airport lighs Units: initialize_lights, update_lights,update_clearance_lights, get_runway_clear, process_clearance****************************************************************/#include <stdio.h>  /* standard input/output */ #include <graph.h>  /*MSC graphics routines */ #include <string.h>  /* MSC string routines */#include <stdlib.h>  /* MSC standard library */ #include <math.h>  /*MSC math library */ #include “sio.h”  /* serial input/output */ #include“lights.h”  /* airport light definitions */ #include “veh.h”  /* vehicledata */ #include “coord.h”  /* coordinate data */ /*-------------------external functions -------------------------*/ void store_wps(charwp_id[12], int wpindex); /*------------------- external variables-------------------------*/ extern VEHICLE_DATA veh[MAX_VEHS]; /*vehicle database */ extern unsigned curr_lights;    /* current lightsettings */ /*------------------- global variables-------------------------*/ short current_clearance; /* set if anyvehicle is cleared */ char veh_cleared[8]; /* vehicle cleared forlanding/takeoff*/ short veh_clear_status; /* clearance status for currvehicle */ short end_of_wps; /* end of clearance/wps *//*---------------------------------------------------------------- UNIT:initialize_lights() DESCRIPTION: initialize_lights sets the airportlights to their default settings - RED for landing and takeoff lightsand OFF for runway intersection (i.e., stop) lights.----------------------------------------------------------------*/initialize_lights() { update_lights(NO_ACTIVITY, RNWY_35);update_lights(NO_ACTIVITY, RNWY_17); update_lights(NO_ACTIVITY,RNWY_24); update_lights(NO_ACTIVITY, RNWY_06); }/*---------------------------------------------------------------- UNIT:update_lights DESCRIPTION: this routine resets the lights on thespecified runway based.----------------------------------------------------------------*/update_lights(int activity_type, int rnwy) { switch (rnwy) { caseRNWY_35 : case RNWY_17 :  switch (activity_type)  { case NO_ACTIVITY :curr_lights = curr_lights & 0xAC; break;  } break; case RNWY_24 : caseRNWY_06 :  switch (activity_type)  { case NO_ACTIVITY : curr_lights =curr_lights & 0x53; break;  } break; case RNWY_INT:  switch(activity_type)  { case NO_ACTIVITY : curr_lights = 0; break;  } break;} /* write new light settings to board */ outp(LIGHT_ADDR, curr_lights);} /*----------------------------------------------------------------UNIT: update_clearance_lights DESCRIPTION: this routine updates thespecified clearance lights for a landing or takeoff operation. Thelanding/takeoff light for the specified runway is enabled, then theremaining landing/taxi lights for both runway ends are disabled.INPUTS:  curr_clear - clearance issued by ATC----------------------------------------------------------------*/update_clearance_lights(short curr_clear) { /* based on currentclearance, affected runway and the current status of the runway'slights, update the lights */  switch (curr_clear)  { case LANDING_35 :if ((curr_lights & LANDING_35) == 0) curr_lights = curr_lights +LANDING_35; break; case LANDING_17 : if ((curr_lights & LANDING_17) ==0) curr_lights = curr_lights + LANDING_17; break; case LANDING_24 : if((curr_lights & LANDING_24) == 0) curr_lights = curr_lights +LANDING_24; break; case LANDING_06 : if ((curr_lights & LANDING_06) ==0) curr_lights = curr_lights + LANDING_06; break; case TAKEOFF_35 : if((curr_lights & TAKEOFF_35) == 0) curr_lights = curr_lights +TAKEOFF_35; break; case TAKEOFF_17 : if ((curr_lights & TAKEOFF_17) ==0) curr_lights = curr_lights + TAKEOFF_17; break; case TAKEOFF_24 : if((curr_lights & TAKEOFF_24) == 0) curr_lights = curr_lights +TAKEOFF_24; break; case TAKEOFF_06 : if ((curr_lights & TAKEOFF_06) ==0) curr_lights = curr_lights + TAKEOFF_06; break; } /* write new lightsettings to board */ outp(LIGHT_ADDR,curr_lights); }/*---------------------------------------------------------------- UNIT:get_runway_clear DESCRIPTION: determines the landing or takeoff flagsetting INPUTS: int rw_id - id of runway char * msg_type - arrival ortakeoff----------------------------------------------------------------*/ intget_runway_clear(int rw_id, char *msg_type) { /**- local variables -**/int clear_stat; /* clearance status */ /* update current clearance(clear_stat) based on the designated runway (rw_id) and type ofclearance (ARRIVAL) or (TAKEOFF) */ switch (rw_id) { case RNWY_35 : if(strstr(msg_type, “ARR”) != NULL) clear_stat = LANDING_35; elseclear_stat = TAKEOFF_35; break; case RNWY_17 : if(strstr(msg_type,“ARR”) != NULL) clear_stat = LANDING_17; elseclear_stat = TAKEOFF_17; break; case RNWY_24 : if(strstr(msg_type,“ARR”) != NULL) clear_stat = LANDING_24; elseclear_stat = TAKEOFF_24; break; case RNWY_06 : if(strstr(msg_type,“ARR”) != NULL) clear_stat = LANDING_06; elseclear_stat = TAKEOFF_06; break; default : clear_stat = SURFACE; }return(clear_stat); }/*---------------------------------------------------------------- UNIT:process_clearance DESCRIPTION: process_clearance parses the clearance ordeparture message issued by the controller via the touch screen.update_clearance_lights is then called to change the specified lightsettings. The message format is : $ATC,002,veh id,waypoint id forarrival (landing) waypoints and $ATC,004,veh id,waypoint id fordeparture (takeoff) waypoints INPUTS:  char clearance_msg[MAX_STR]----------------------------------------------------------------*/process_clearance(char clearance_msg[MAX_STR]) { /**- local variables-**/ char wp_id[12];   /* waypoint id     */ char *token;   /* characterfield from ATC msg     */ int rw_id;   /* id of runway cleared foroperation   */ int veh_index;   /* index into veh database for currentveh     */ int slen;   /* string length       */ int i;   /*counter       */ /* parse clearance message */ token =strtok(clearance_msg,“,”);  /* $ATC */ token = strtok(NULL,“,”);     /*message type */ token = strtok(NULL,“,”);     /* vehicle id */strcpy(veh_cleared,token); token = strtok(NULL,“,”);     /* waypoint id*/ /* extract waypoint information */ slen = strlen(token) − 2; for (i =0; i < slen; i++) wp_id[i] = token[i]; wp_id[i] = ‘\0’; /* get runway idfrom waypoint information */ if (strstr(wp_id,“35”) != NULL) rw_id =RNWY_35; else if (strstr(wp_id,“24”) != NULL) rw_id = RNWY_24; else if(strstr(wp_id,“17”) != NULL) rw_id = RNWY_17; else if(strstr(wp_id,“06”) != NULL) rw_id = RNWY_06; else rw_id = 0; /* findvehicle in vehicle database */ veh_index = find_veh_index(veh_cleared);if (veh_index != −1) /* if vehicle found in database */ { /* setclearance based on message type and selected runway */ current_clearance= current_clearance − veh[veh_index].clear_status;veh[veh_index].clear_status = get_runway_clear(rw_id, wp_id);current_clearance = veh[veh_index].clear_status + current_clearance; /*extract and store waypoint data */store_wps(wp_id,veh[veh_index].wpindex); veh[veh_index].currwp = NO_WP;end_of_wps = FALSE; /* update lights immediately for arrival aircraft */if (strstr(wp_id,“ARR”) != NULL)update_clearance_lights(current_clearance); } /* if vehicle in database*/ }

Clearance Delivery

[0636] If the vehicle is entering or inside a runway zone and thevehicle has a clearance, a runway incursion is not detected. A clearanceis issued by the AC&M operator using the ARRIVAL WAYPOINTS, DEPARTUREWAYPOINTS or SURFACE WAYPOINTS functions.

[0637] When a clearance is issued, a global CURRENT_CLEARANCE flag isupdated. The CURRENT_CLEARANCE flag is used to maintain the currentairport light settings. A separate clearance status flag is alsomaintained in the vehicle database for each vehicle. As the vehicleapproaches a runway zone, its clearance status flag is read to determinewhether a runway incursion condition should be generated. Clearances areterminated automatically when the vehicle reaches the last waypoint.Clearances may also be manually cleared by the AC&M operator through theCLEAR PATH WAYPOINTS function. When the clearances are terminated, theglobal CURRENT_CLEARANCE flag and individual vehicle clearance flags areupdated.

ECEF Waypoint Navigation

[0638] After waypoints have been issued to a vehicle or vehicles, theAC&M performs a set of navigation functions, mirroring those performedon board the vehicle using the ADS position reports. A set of waypointsis maintained for each cleared vehicle. The vehicle's current 3-D rangeto the waypoint and cross track error is computed for each subsequentADS report. A determination as to whether the vehicle is on or offcourse is also made. If an off course condition is detected, a warningmessage is displayed to the operator in the AC&M's Alerts window.

[0639] To support the AC&M's mirrored navigation processing, thefollowing fields are maintained in the vehicle database:

[0640] Waypoint Index

[0641] Current Waypoint

[0642] Cross Track Error

[0643] 3D Range to Waypoint

[0644] Wrong Way Indicator

[0645] The Waypoint Index is the ID of the waypoint list assigned to thevehicle and the Current Waypoint is the waypoint the pilot is navigatingtowards.

[0646] At any time after the assignment of waypoints to the vehicle, thevehicle's 3-D range to the waypoint, cross track error, currentwaypoint, speed and heading information may be displayed in the MC&Rwindow using the VEHICLE DATA function.

[0647] GRAPHICS PROCESSOR AND AC&M INTERFACE

[0648] The Graphics Processor (GP) 122 interfaces to the AC&M Processor121 via a dedicated communication link 123. The GP is currently based ona 66 mHz 486 processor with a VESA Video Local Bus. This processorperforms the following functions:

[0649] Receives graphics commands from AC&M

[0650] Interprets graphics commands

[0651] Performs the graphic display functions

[0652] Provides situational awareness capability

[0653] Manages the view and content of the display presentation

[0654] Maintains local map-based waypoint, zone and map layer databases

[0655] Interface with large graphics display hardware

[0656] Two types of messages are received by the GP:

[0657] (1) vehicle position messages

[0658] (2) display commands

[0659] Upon receipt of an ADS report, the AC&M Processor converts thevehicle's ECEF X,Y,Z position to the map's coordinate system if requiredand determines the appropriate map layer for the vehicle based on thevehicle's type and any collision or zone incursion conditions. If thevehicle is moving, the newly formatted message is sent to the GP.Stationary vehicle's are not redisplayed in the map but remain displayedin their last reported position. The message format is shown below:

$TRK,vehicle id,map layer,map x, map y, mapz coordinates<CR><LF>

[0660] Display commands are also generated by the AC&M Processor 121 andsent to the GP 122. Numerous AC&M commands, including ARRIVAL WAYPOINTS,DEPARTURE WAYPOINTS, SURFACE WAYPOINTS, CLEAR PATH WAYPOINTS, DISPLAYVIEW, VEHICLE FILTER and LAYER FILTER affect the display presentation onthe GP. An acknowledgment is returned to the AC&M Processor 121 when adisplay command message is received by the GP 122.

[0661] LAYER ASSIGNMENTS

[0662] The GP 122 supports up to 256 unique layers which are used forthe display and segregation of graphic information. The layerassignments are provided below. MAP LAYER ASSIGNMENTS LAYER #DESCRIPTION MODE 0-2 AIRPORT MAP RUNWAYS, ALWAYS TAXIWAYS, TRAVEL PATHS3 RANGE RINGS ON DEMAND 4 EXPANSION TBD 5 RANGE RINGS, 5 MILE ON DEMANDINCREMENTS 6-8 EXPANSION TBD 9 AIRPORT LIGHTING ON DEMAND SYSTEMS (RNWY35) 10 AIRPORT LIGHTING ON DEMAND SYSTEMS (RNWY 24) 11 TRACKED SURFACEALWAYS VEHICLES (LIMITED ACCESS) 12 TRACKED SURFACE ALWAYS VEHICLES(FULL ACCESS) 13 TRACKED DEPARTURE ALWAYS AIRCRAFT 14 TRACKED ARRIVALALWAYS AIRCRAFT 15-19 EXPANSION TBD 20 ARRIVAL WAYPOINTS ON DEMAND 21DEPARTURE WAYPOINTS ON DEMAND 22 SURFACE WAYPOINTS ON DEMAND 23 CUSTOMWAYPOINTS ON DEMAND DEFINITION 24 EXPANSION TBD 25 AIRPORT SURFACE ZONESON DEMAND 26 WEIGHT LIMITED ZONES ON DEMAND 27 RESTRICTED TRAVEL AREA ONDEMAND (WINGSPAN, ETC.) 28 AIRSPACE HAZARD ZONES ON DEMAND 29 OPENCONSTRUCTION ZONES ON DEMAND 30 CLOSED CONSTRUCTIONS ON DEMAND ZONES31-60 EXPANSION TBD 61 WATCH LAYER (COLOR = ALWAYS YELLOW) 62 WARNINGLAYER (COLOR = ALWAYS RED)

[0663] VEHICLES

AC&M System Functional Matrix

[0664] Many of the functions performed at the AC&M Processor are alsoperformed on board the vehicles. Three vehicles, equipped with varyingconfigurations of hardware and software, have been used in a number ofprototype demonstrations. The matrix below lists the major functions andthe vehicles on which they are performed. VEHICLE FUNCTIONAL MATRIX FULLLIMITED ACCESS ACCESS FUNCTION AC&M AIRCRAFT VEHICLE 1 VEHICLE 2 Receive& process N Y Y Y DGPS corrections Formats and N Y Y Y transmits ADSposn & vel. data Receives remote Y N Y N ADS messages Displays ADS Y N YN positions in map display Performs dynamic Y N Y N collision processingPerforms zone Y Y Y Y incursion processing Performs runway Y N N Nincursion processing Controls airport Y N N N lights Formats ATC Y N N Ncommands Receives ATC N Y Y Y commands Performs waypoint Y Y Y Nnavigation Displays current N Y Y N position in moving map display

[0665] Hardware block diagrams for each of the three prototype vehicletypes are provided in the figures which follow, starting with theAircraft System FIG. 24.

[0666] Differential GPS data is provided by a GPS GOLD DGPS receiver 124and a differential data link 125. GPS position, velocity, and timeinformation is supplied to the dual 486 based processing unit. The first486 processor, or Navigation (NAV) Processor 126, receives GPS Receiver124 information and performs the following functions:

[0667] Coordinate conversions from Lat/Lon/MSL to ECEF X, Y, Z

[0668] Position projections

[0669] Zone and runway incursion checking

[0670] Map layer control

[0671] General ECEF waypoint navigation and on/off course processing

[0672] ECEF-based precision landing navigation

[0673] Access to waypoint and zone databases

[0674] Transmission of graphic instructions to second 486 processor 127

[0675] Broadcast of position and velocity data over ADS datalink 128

[0676] Control of communication digital datalinks

[0677] Support for monochrome flat panel display 129

[0678] The second 486 processor, the Aircraft Graphics Processor (AGP)127, receives graphics instructions from the NAV Processor 126 andperforms the following functions:

[0679] Graphics command translations and interpretations

[0680] Graphic display functions

[0681] Display presentation view and content management

[0682] Support for monochrome flat panel display 130

[0683] The functions supported in the aircraft are actually a slightlymodified version of those performed by the AC&M Subsystem. The use ofcommon hardware and operational software elements simplified theprototype demonstration development efforts.

[0684] The full access surface vehicle (Vehicle #1) high level blockdiagram is provided in FIG. 25.

[0685] Again, differential GPS data is provided by a DGPS receiver 131and a differential data link 132. GPS position, velocity, and timeinformation are supplied to the dual 486 based processing unit. Thefirst 486 processor, the Navigation Processor (NAV) 133, receives GPSinformation and performs the following functions:

[0686] Coordinate conversions from Lat/Lon/MSL to ECEF X, Y, Z

[0687] Position projections

[0688] Collision prediction processing

[0689] Zone and runway incursion checking

[0690] Layer control

[0691] General ECEF waypoint navigation (optional)

[0692] Access to vehicle, waypoint and zone databases

[0693] Transmission of graphic instructions to second 486 processor 134

[0694] Broadcast of position and velocity data over ADS datalink 135

[0695] Receipt of remote ADS messages from other vehicles

[0696] Control of communication digital datalinks

[0697] Support for flat panel LCD display

[0698] The second 486 processor, the Vehicle Graphics Processor (VGP)134 receives graphics instructions from the NAV Processor 133 andperforms the following functions:

[0699] Graphics command translations and interpretations

[0700] Graphic display functions

[0701] Situational awareness capability

[0702] Display presentation view and content management

[0703] Support for flat panel LCD display 136

[0704] The functions supported in the full access surface vehicle areidentical to those performed in the aircraft with a couple of additions.The full access vehicle receives remote ADS messages from other vehiclesoperating within the airport space envelope. This information is used toprovide a situational awareness capability on board the vehicle. Fullcollision detection processing is also implemented.

[0705] The limited access surface vehicle (Vehicle #2) is equipped withdeveloped hardware and software as shown in FIG. 26.

[0706] Since no graphic display is provided on Vehicle #2, a single386-based processor 137 is utilized. Again, Differential GPS data isprovided by an on board DGPS receiver 138 and a differential data link139. GPS position, velocity, and time information is supplied to the 386based processing unit 137 which performs the following functions:

[0707] Coordinate conversions from Lat/Lon/MSL to ECEF X, Y, Z

[0708] Position projections

[0709] Zone and runway incursion checking

[0710] Access to zone database

[0711] Sounds audible warning when zone incursion is detected 140

[0712] Broadcast of position and velocity data over ADS datalink 141

[0713] The functions supported in Vehicle #2 are actually a subset ofthose supported in the aircraft and Vehicle #1.

COMMUNICATIONS

[0714] Each vehicle is equipped with a VHF/UHF radio capable of fullduplex communications. The radio interfaces to an integrated modem/GPSinterface card. The radio modem is used to receive differentialcorrections, ADS messages, and ATC command messages forwarded by theCOMM Processor. Local GPS messages are received by the vehicle'sNavigation (NAV) processor. The GPS position and velocity data isconverted to the ECEF coordinate frame, reformatted and transmitted tothe AC&M Processor over the same radio.

Navigation Processor and Navigation

[0715] Navigation functions are performed on board the vehicle whenwaypoints are received from the AC&M Processor via the VHF datalink. Twonavigation screens are provided, a cross hairs display for airborneapplications and a map-based display for ground operations.

[0716] Upon receipt of the waypoint message from the AC&M Processor, thewaypoint id is extracted and used to identify the predefined waypointpath. The waypoints are automatically loaded into the vehicle's ECEFnavigation system and drawn into the vehicle's map display. FIG. 27shows the airborne navigation display produced with the previouslylisted software routines.

[0717] The navigator display format is unique since it providesconventional course, bearing and range information and actual positionwith respect to the true course. The display portion on the right sideof the screen is driven by NEU surface parameters while the display atthe left is driven directly by ECEF X, Y, Z parameters. This displayformat may be used for all phases of flight.

[0718] The algorithms for 3-D range to the waypoint, transitioning tothe next waypoint, cross track error, on/off course and wrong waydetermination are identical to those performed at the AC&M Processor.

[0719] For ground taxi operations, map-based waypoint navigation wasfound to be preferable. FIG. 8 shows a waypoint path from the Crash,Fire and Rescue (CFR) Station to the East Terminal Ramp drawn in the onboard digital map display.

[0720]FIG. 9 depicts the predefined waypoint path for a departure onRunway 35.

Zones Processing

[0721] All surface vehicles are capable of performing static zoneincursion processing. The zone processing algorithms are identical tothose implemented at the AC&M system with the addition of an audibletone generated when an incursion occurs.

Collision Detection Processing

[0722] The fully equipped vehicle (FEV) is capable of performingcollision prediction processing based on the vehicle's current position(and velocity) and the remote vehicles' ADS messages.

[0723] As the ADS messages are received, they are parsed and stored inthe local vehicle database. Collision processing is performed eachsecond, upon receipt of the FEVs GPS position and velocity data. Aftereach GPS update, projections are performed on the FEV's current positionand compared to the projected positions for each vehicle stored in thelocal database. In the same manner as described for the AC&M Processor,potential collision watch and warning conditions are detected betweenthe FEV and other vehicles. However, collisions between two remotevehicles are not detected. Collisions tests are only performed withrespect to the FEV itself and those in its vicinity.

Graphic Processor and Moving Map Display

[0724] Both the FEV and the aircraft are capable of displaying theircurrent position with respect to an on board moving map display. As thevehicle's position approaches the edge of the map display, the map isautomatically panned and redrawn with the vehicle centered in thedisplay. When the vehicle is on the airport surface, the map is drawnwith a north orientation at a 0.25 mile plan view perspective. When thevehicle is more than one mile from the center of the map, the map isautomatically redrawn at a ten (10) mile scale.

Situational Awareness

[0725] The FEV is capable of displaying the positions of remote vehiclepositions in the on board moving map display. As ADS messages arereceived from the COMM Processor, the remote vehicles' positions arechecked to see if they would appear on the current display view. If thepositions are outside of the current view, they are discarded. Positionswithin the current view are drawn into the map display.

Layer—Color Control

[0726] As at the AC&M processor, the FEV's situational awareness displayuses color cues to indicate vehicles in a collision or zone incursioncondition. As ADS and GPS messages are received and processed by the onboard NAV Processor, graphics messages are formatted and sent to thelocal Graphics Processor (GP). These graphics messages are identical tothose created at the AC&M Processor and include the vehicle id, layer idand map x,y,z position.

[0727] Coordinate Conversions Software Example

[0728] OVER COMING ERROR SOURCES

Map Temporal Differential Correction

[0729] Map temporal differential corrections are a simple and effectivemeans of reducing error sources in GPS operation for short periods oftime when Selective Availability is not active. FIG. 31 depicts the maptemporal correction elements.

[0730] Map temporal corrections utilize at least one precisely surveyedlocation in the local area. The surveyed location may be determined froma monument marker or may be determined using a highly accurate digitalor paper map. A GPS receiver and (optionally) a processing computer areco-located at the known location with the GPS antenna carefullypositioned at the survey point. The receiver/computer remains at theknown location for a period of time and, when enough data has beencollected, determines pseudo range correction and pseudo range ratefactors. These correction factors may then be applied to thedifferential GPS receiver to determine a corrected position. Thesefactors are used in subsequent position determinations until another maptemporal correction is applied.

[0731] Map temporal corrections are the simplest form of closed loopdifferential correction. As the name implies, temporal correctionsdegrade with time as the receiver moves within the local area. SAsignificantly reduces the benefits of a temporal differential correctionapproach. When SA is not active, the short term (30 minute) accuracy ofthis technique is very good (a meter or two), since all error sourcesare reduced. One additional limiting factor is that the same satellitesmust be used during roving operations as those used at the surveyedlocation. This may be accomplished through software control to ensure a‘selected’ set of satellites are used for a given GPS session.

Regional Differential Corrections and Differential Overview

[0732] Real time differential correction techniques compensate for anumber of error sources inherent to GPS. The idea is simple in conceptand basically incorporates two or more GPS receivers, one acting as astationary base station and the other(s) acting as roving receiver(s).The differential base station is “anchored” at a known point on theearth's surface. The base station receives the satellite signals,determines the errors in the signals and then calculates corrections toremove the errors. The corrections are then broadcast to the rovingreceivers.

[0733] Real time differential processing provides accuracies of 10.0meters or better (typically 1.0-5.0 meters for local differentialcorrections). The corrections broadcast by the base station are accurateover an area of about 1500 km or more. Typical positional degradation isapproximately a few millimeters of position error per kilometer of basestation and roving receiver separation. FIG. 32 shows the basic elementsfor real time differential GPS (DGPS) operations.

[0734] Through the implementation of local differential GPS techniques,SA errors are reduced significantly while the atmospheric errors arealmost completely removed. Ephemeris and clock errors are virtuallyremoved as well.

[0735] ERROR SOURCES CORRECTED OR REDUCED BY DGPS USER RANGE ERRORS(URE) 1 SIGMA MAGNITUDES WITHOUT DGPS WITH DGPS SATELLITE CLOCK & NAV.2.7 0 EPHEMERIDES & PREDICTION 2.7 0 ATMOSPHERIC IONOSPHERIC 9.0 0TROPOSPHERIC 2.0   .15* SELECTIVE AVAILABILITY 30.0# 0 TOTAL RSS 31.6   .15

[0736] # To counteract the effects of SA, differential corrections mustbe generated, transmitted and utilized in the GPS receiver at a ratesufficient to compensate for the rate of change of SA.

[0737] Differential GPS can introduce an additional error, if notemployed properly. The age of the differential correction must bemonitored at the GPS receiver. As the differential correction ages, theerror in the propagated value increases as well. This is particularlytrue for ‘virulent’ strains of SA where the errors introduced slewquickly over very short time intervals.

Operational Elements

[0738] The precisely surveyed location of the GPS antenna is programmedinto the reference station as part of its initial installation and setup procedures. Industry standard reference stations determine pseudorange and delta range based on carrier smoothed measurements for allsatellites in view. Since the exact ECEF position of the antenna isknown, corrections may be generated for the pseudo range and delta rangemeasurements and precise time can be calculated.

[0739] Naturally occurring errors are, for the most part, slow changingand monotonic over the typical periods of concern. When SA is notinvoked, delta range corrections provide a valid method of improvingpositional accuracy at the roving receivers using less frequentcorrection broadcasts. With the advent of SA and its random, quickchanging non-monotonic characteristics, delta range corrections becomesomewhat meaningless and may actually degrade the system performanceunder some conditions.

[0740] As shown previously in FIG. 32, the DGPS correction messages arebroadcast by the reference station and received by the roving receivers.The corrections are applied directly to the differential GPS receiver.The DGPS receiver calculates the pseudo range and the delta rangemeasurements for each satellite in the usual manner. Prior to performingthe navigation solution, the received pseudo range and delta rangecorrections are applied to the internal measurements. The receiver thencalculates corrected position, velocity and time data. Typical DGPSposition and velocity performance is presented in the table below.

[0741] COMPARISON OF TYPICAL GPS POSITION AND VELOCITY

[0742] MEASUREMENTS USING COMMERCIAL NAVIGATION TYPE RECEIVERS

[0743] (ACCURACIES ARE A FUNCTION OF CORRECTION AGE)

[0744] THIS EXAMPLE USES CORRECTION AGE=5 SECONDS COMPARISON OF TYPICALGPS POSITION AND VELOCITY MEASUREMENTS USING COMMERCIAL NAVIGATION TYPERECEIVERS (ACCURACIES ARE A FUNCTION OF CORRECTION AGE) THIS EXAMPLEUSES CORRECTION AGE = 5 SECONDS WITHOUT DGPS WITH DGPS CODE RCVR CARRIERRCVR CODE RCVR CARRIER RCVR 2-D POSITION <100 M <40 M <10 M <2 M 3-DPOSITION <176 M <80 M <18 M <4 M VELOCITY knots <10 KN <5 KN <.1 KN <.1KN TIME* <300 ns <100 ns <100 ns <50 ns

[0745] Since differential GPS eliminates most GPS errors, it providessignificant improvements in system reliability for life critical airportoperations. Short term and long term drift of the satellite orbits,clocks and naturally occurring phenomenon are compensated for bydifferential GPS as are other potential GPS satellite failures.Differential GPS is mandatory in the airport environment from areliability, accuracy and fault compensating perspective.

[0746] As with autonomous GPS receiver operation, multipath is apotential problem. The differential reference station cannot correct formultipath errors at the roving receiver(s). Antenna design and placementconsiderations, and receiver design characteristics remain the bestsolutions to date in the minimization of multipath effects.

[0747] DGPS provides the means to eliminate most GPS system errors. Theremaining errors are related to receiver design and multipath. Not allGPS receivers and reference stations are created equal, some aredistinctly better than others. The selection of the reference stationand the roving receivers has a significant effect on the overall systemaccuracy.

Compensating for Receiver Error

[0748] Receiver errors are not corrected using an ‘open loop’differential correction method as described above. These errors may bereduced when a ‘closed loop’ differential technique is employed. FIG. 33presents a high level block diagram of a ‘closed loop’ differentialsystem.

[0749]FIG. 33 has additional elements over the standard differentialsystem configuration. A second GPS antenna is installed at a preciselysurveyed antenna location and a stationary GPS receiver is co-locatedwith the reference station. This receiver accepts differentialcorrection inputs generated by the reference station. The stationary GPSreceiver incorporates the pseudo range corrections in the normal mannerand determines DGPS position and velocity. The corrected position andvelocity are then compared to the stationary receivers known positionand velocity (0,0,0). The ECEF delta position and velocity data are thenused by the reference station processing to further refine the pseudorange and delta range corrections which are broadcast to the rovingreceivers. Processing software which minimizes the position and velocityerrors is used. This technique requires that the roving receivers beidentical to the stationary GPS receiver located at the referencestation site. That is, the roving receivers must exhibit receiver errorssimilar to those on the stationary DGPS receiver.

[0750] INTEGRITY AND MULTI-SENSOR SYSTEMS

[0751] The issues of integrity and fault monitoring are a major concernsfor any technology considered for the life critical application of airtransport and air traffic control. The integration of GPS with othertechnologies provides a higher degree of fault detection capability, apotentially improved GPS navigational performance, and the potential oflimited navigation support should a catastrophic GPS failure occuraboard the vehicle.

[0752] The integration of GPS with an inertial system can be used toimprove the dynamic performance of the navigation solution. Dynamicsensors may provide jerk, acceleration and velocity information to aidin the navigation solution. Sole means inertial navigation may be usedin conjunction with GPS. The integration of GPS with inertial systemsusually require 12 (or higher) state Kalman filter solutions techniques.

[0753] The concept of Receiver Autonomous Integrity Monitoring (RAIM) isaccepted as a potential integrity monitoring system. The RAIM conceptrequires that the GPS receiver and/or navigation system include therequired “smarts” to diagnose its own health using additionalsatellites, redundant hardware and specialized internal softwareprocessing. RAIM standards are currently being developed for industryapproval.

[0754] When combined with other sensors such as WAAS, inertial, baroaltimeter and internal RAIM processing, GPS will have superior accuracy,fault tolerance and fault detection capability.

[0755] FAULT TOLERANCE AND HIGH AVAILABILITY

[0756] Any system which controls life critical operations at an airportmust support fault tolerance and high availability. At the same time,the system must be cost effective and support technology insertion. Highsystem availability may be achieved through a custom design processutilizing selected and screened components for high Mean Time BetweenFailure (MTBF). Alternatively, high availability may be achieved throughsystem redundancy using components of non-custom, commercial-off-the-shelf design. The following paragraphs introduce a few of the conceptswhich are later utilized in the system design analysis.

[0757] AVAILABILITY: Availability is defined as the probability that asystem will operate to specification at any point in time, whensupported with a specific level of maintenance and spares.

[0758] MEAN TIME BETWEEN FAILURES (MTBF): The mean time a piece ofequipment will remain operational before it is expected to fail.

[0759] RELIABILITY: The inherent probability that a piece of equipmentor hardware will remain operational for a period of time (t). It isexpressed as follows:

−(t/MBTF)

R(t)=e

[0760] TRAVEL TIME: The travel time is measured from the time of failureto the time the repair technician and required spare parts arrive at thefailed equipment.

[0761] MEAN TIME TO RECONFIGURE (MTTC): The mean time a system isinoperable as measured from the time of failure to the time of fulloperation. Typically, reconfiguration time involves bringing on lineredundant systems in an effort to provide continued service.

[0762] MEAN TIME TO REPAIR AND CERTIFY (MTTRC): The mean time of theactual repair and recertification activities as measured from the timeof arrival of the failed equipment to the time which the equipment is online, certified and declared operational.

[0763] MEAN TIME TO REPAIR (NMR): MTTR is the sum of TRAVEL+MTTC+MTTRC.

[0764] AVAILABILITY EXAMPLE

[0765] The following analysis builds upon elements of the systemcomposed of off the shelf components arranged in a redundantconfiguration. Commercial industrial single board computers areconnected with other commercial elements in the manner as shown in theFIGS. 28, 29, 30. This approach provides cost effectiveness, COTStechnology insertion, declining COTS life cycle costs and highavailability. The analysis starts with no design redundancy FIG. 28, andends describing a two controller station redundant architecture FIG. 30.

[0766] This example will determine the overall reliability andavailability of the architecture shown in FIG. 28. The requirement forsystem availability for this terminal area system comes from the FAAAdvanced Automation Program (AAS). The AAS program defines the systemyearly availability to be 0.99995 determined using a 2 hour travel timewhich is added to any other system down time. The major elements of theairport system shown in FIG. 28. KEY OPERATIONAL PARAMETERSAVAILABILITY * AVAIL = 0.99995 TRAVEL TIME (HRS) * TRAVEL = 2.0 TIME TOAUTO CONFIGURE (HRS) MTTC = .025 90 SECONDS MEAN TIME TO REPAIR ANDCERTIFY (HRS) MTTRC = .25 (TESTED SPARES, FAULT ISOLATED TO LRU) MEANTIME TO REPAIR (MTTR) MTTR = MTTRC + MTTC + TRAVEL  MTTR = 2.275

Specific Component Parameters

[0767] SINGLE BOARD COMPUTER 142, 143 MEAN TIME BETWEEN FAILURES (FHRS)

SBC:=90000 ${RSBC} = {{^{- \frac{YR}{SBC}}\quad {RSBC}} = 0.907254}$

[0768] DIGITAL RADIO TRANSCEIVER 144 MEAN TIME BETWEEN FAILURES (HRS)

XCVR.=75000${RXCVR} = {{^{- \frac{YR}{XCVR}}\quad {RXCVR}} = 0.889763}$

[0769] TOUCH SCREEN 145 MEAN TIME BETWEEN FAILURES (HRS)

TOUCH.=100000${RTOUCH} = {{^{- \frac{YR}{TOUCH}}\quad {RTOUCH}} = 0.916127}$

[0770] LOW VOLTAGE DC POWER SUPPLY 146 MEAN TIME BETWEEN FAILURES (HRS)

LVPS.=500000${RLVPS} = {{^{- \frac{YR}{LVPS}}\quad {RLVPS}} = 0.982633}$

[0771] FLAT SCREEN DISPLAY 147 MEAN TIME BETWEEN FAILURES (HRS)

DIS=75000 ${RDIS} = {{^{- \frac{YR}{DIS}}\quad {RDIS}} = 0.889763}$

[0772] AIRPORT LIGHTING UNIT 148 MEAN TIME BETWEEN FAILURES (HRS)

[0773] Interface only, no light bulbs or individual light switches

LITE.=250000${RLITE} = {{^{- \frac{YR}{LITE}}\quad {RLITE}} = 0.965567}$

[0774] REDUNDANT ARRAY of INEXPENSIVE DISKS (RAID 149 MTBF (HRS)

RAID=150000${RRAID} = {{^{- \frac{YR}{RAID}}\quad {RRAID}} = 0.943273}$

[0775] LOCAL AREA NETWORK 150 MEAN TIME BETWEEN FAILURES (HRS)

LAN=87600 ${RLAN} = {{^{- \frac{YR}{LAN}}\quad {RLAN}} = 0.904837}$

[0776] KEYBOARD 151 MEAN TIME BETWEEN FAILURES (HRS)

KBD:=75000 ${RKBD} = {{^{- \frac{YR}{KBD}}\quad {RKBD}} = 0.889763}$

[0777] DIFFERENTIAL BASE STATION 152 MEAN TIME BETWEEN FAILURES (HRS)

DIFF.=100000${RDIFF} = {{^{- \frac{YR}{DIFF}}\quad {RDIFF}} = 0.916127}$

[0778] This particular analysis is for a single controller station,multiple stations could be used simply by duplicating the deignelements. The controller must have the following capabilities to performhis airport duties:

[0779] 1. have full duplex voice and data communications

[0780] 2. a controlling AC&M display and graphic display

[0781] 3. a command touch screen capability or keyboard

[0782] 4. differential GPS for all navigation

[0783] 5. airport lighting interface (independent bulbs and switches mayfail without loss of function)

[0784] The minimal set of controller actions require the followinghardware and associated software to be operational.

[0785] 1. radio transceiver (voice and data function)

[0786] 2. AC&M display, SBC server, and RAID

[0787] 3. Graphic display, SBC,

[0788] 4. a low voltage power supply

[0789] 5. a command and control touch screen or a keyboard

[0790] 6. minimal configuration operational software

[0791] 7. a LAN assembly

[0792] 8. a differential GPS base station

[0793] 9. a airport lighting interface

[0794] The hardware elements can be connected in a minimal hardwareconfiguration and the overall availability can be compared to thespecified value of 0.99995

[0795] INITIAL SERIES RELIABILITY

RINT:=RSBC²·RXCVR·RTOUCH·RLVPS·RDIS²·RRAID RLAN·RDIFF·RLITE RKBD

RINT=0.350629

[0796] The initial MTBF for the series string is determined below.${MTBFINT} = {{\frac{- ({YR})}{\ln ({RINT})}\quad {MTBFINT}} = 8358.56594}$

[0797] Initial availability based upon series minimum configuration is$\frac{MTBFINT}{{MTBFINT} + {MTTR}} = 0.999728$

[0798] As expected availability does not meet the specification, systemredundancy will be necessary to achieve the design goal. To meet therequired availability a system MTBF of about 45,000 hours will benecessary with a 2.275 hour mean time to repair. A new architecture isshown in FIG. 29.

[0799] AIRPORT SYSTEM, SINGLE REDUNDANT CONTROLLER STATION

[0800] Redundant radio transceivers will be necessary since a singlepoint failure is unacceptable in this component. Parallel radiotransceiver reliability is determined below:

RXCVRP−RXCVR+RXCVR−RXCVRXCVR RXCVRP=0.987848

[0801] Redundant LVPS are required for the same reason.

[0802] RLVPSP RLVPS RLVPS (RLVPS·RLVPS) RLVPSP=0.999698

[0803] Redundant Local Area Networks are also required, since a singlepoint failure can not be tolerated in communications between the AC&MSBC and Graphic SBC.

[0804] RLANP=RLAN+RLAN−(RLAN·RLAN) RLANP=0.990944

[0805] Redundant Differential GPS are also required, since a_singlepoint failure can not be tolerated in airport navigation functions.

[0806] RDIFFP=RDIFF+RDIFF−(RDIFF·RDIFF) RDIFF=0.916127

[0807] Redundant airport lighting control interfaces are required.

[0808] RLITEP=RLITE RLITE (RLITE·RLITE) RLITEP=0.99814

[0809] The keyboard and the touch screen provide the same capability,hence may be treated as a parallel redundant system element. Thekeyboard/touch screen combination is found below:

RTOU_KBD=RKBD+RTOUCH−(RKBD·RTOUCH) RTOU_KBD=0.990754

[0810] An extra display surface will be added to display information.This display capability will be used should a failure occur in an AC&Mdisplay or in a graphic situation display. A 2 of 3 display scenario isused for successful mission completion. Should a failure occur autoreconfiguration must occur within the specified time allocation. Todetermine exactly what the 2 out of 3 display process represents, aprobability analysis is performed. The probability is determined fromthe series elements which make up the display function. One displaychannel may fail while the two others provide the necessary information.The third display is used to provide non mission critical informationwhen acting as a hot spare.

[0811] SERIES DISPLAY CHANNEL ELEMENTS

[0812] RSDIS=RDIS·RSBC·RRAID RSDIS=0.761448

[0813] In the 2 of 3 scenario the possible operating combinations mustadd to one; meaning the probability of all of the possible operatingmodes must add to 1. The operating combinations are identified below:

[0814] 1. all 3 serial display channels are operational

[0815] 2. one channel is down and the other two are operational

[0816] 3. two channels are down and only one is operating

[0817] 4. all channels are down

[0818] UNRELIABILITY IS DEFINED AS:

Q.=1−RSDIS

[0819] THE PROBABILITY IS DEFINED BELOW:

RTOTAL=RSDIS ³+3·RSDIS ² ·Q+3·RSDIS·Q² +Q ³

RTOTAL=1 All combinations do add to 1

[0820] TWO OF THREE OPERATIONAL RELIABILITY IS

R2OF3=RSDIS³+3·RSDIS²·Q+0+0  R2OF3=0.856429

[0821] Now the overall system reliability and availability functions maybe evaluated.RFINAL := R2OF3 ⋅ RXCVRP ⋅ RLVPSP ⋅ RTOU_KBD ⋅ RLANP ⋅ RDIFFP ⋅ RLITEPRFINAL = 0.82354  ${MTBFFIN} = {{\frac{- ({YR})}{\ln ({RFINAL})}\quad {MTBFFIN}} = 45121.264957}$$\quad {{FINALAV} = {{\frac{MTBFFIN}{{MTBFFIN} + {MTTR}}\quad {FINALAV}} = 0.99995}}$

[0822] From a hardware perspective the system meets requirements. Thesystem software must be able to detect hard and soft failures and mustbe able to fault isolate the failed device. Parallel hardware redundancyand “smart” software provide the necessary fault monitoring, faultcontainment and fault identification to the LRU level. Operationalsoftware is tailored to the specific application, but the hardware isbased upon COTS standards to allow for future technology insertion andcost effective replacement.

[0823] Multiple controller stations may be added to support largerairport systems. In this case a slightly different architecture isutilized. Common elements are shared by multiple stations. In the 2station architecture shown parallel differential GPS base stations,parallel lighting control interfaces, parallel Local Area Networks andparallel transceivers are utilized. Since a redundant capability isprovided with multiple controller stations consisting of 2 of 3 scenarioincreased availability is provided as shown in FIG. 30.

[0824] THE RELIABILITY OF THE TWO CONTROLLER STATION IS FOUND BELOW

RSTAT=R2OF3·RTOU_KBD·RLVPSP RSTAT=0.848255

The Reliability of the Shared Elements Follows

REXT=RLVPSP·RXCVRP·RDIFFP·RLITEP·RLANP REXT=0.97057

[0825] RELIABILITY OF THE TWO PARALLEL 2 OF 3 CONTROLLER STATIONS IS

[0826] RSTATP=RSTAT+RSTAT−(RSTAT·RSTAT) RSTATP=0.976973

[0827] RELIABILITY OF THE TWO CONTROLLER STATION AIRPORT SYSTEM IS

[0828] RTOT=RSTATP·REXT RTOT=0.948222

[0829] SYSTEM TOTAL MTBF IS${MTBF} = {{\frac{- ({YR})}{\ln ({RTOT})}\quad {MTBF}} = 164763.651199}$

[0830] SYSTEM AVAILABILITY IS${AVAIL} = {{\frac{MTBF}{{MTBF} + {MTTR}}\quad {AVAIL}} = 0.999986}$

[0831] Further availabilty improvements and cost reduction may berealized when configured with multiple controller stations. The 2 of 3display channel operation may be reduced to 2 single display channelsand RAIDS may be eliminated while still meeting availability goals whenoperating with multiple redundant reconfigurable controller stations.

[0832] AIRPORT LAYOUT PLAN

[0833] The U.S. FAA recommends the development of digitized AirportLayout Plans (ALPs). In an ALP, the existing and proposed land andfacilities required in the operation and development of the airport areprovided in a scaled drawing. Each ALP should include the followinginformation:

[0834] airport facilities—runways, taxiways, ramps, service roads,navigation aids, and buildings

[0835] airspace matters—existing and planned approach/missedapproach/departure procedures, special use and controlled airspace,control zones and traffic patterns

[0836] obstructions to air and ground navigation

[0837] airport topography

[0838] precise airport monumentation

[0839] If designed properly, the ALP should be suitable for use inairport master plan activities, emergency work, maintenance, navigationand ATC.

GPS Compatible Monumentation

[0840] Airport ALP generation or mapping activities may use any numberof map coordinate systems based on a number of earth datums or ellipsoidreferences. Standardization of the mapping techniques and references arekey in the development of any successful multi-use mapping program. Inaddition to the selection of a standard reference system, the interfaceto the local area surrounding the airport must be addressed. Accuratecross referenced monumentation points are necessary to allow for asmooth transition between the local coordinate system and the one usedin the airport maps or in the navigation system. In the U.S., localState Plane Coordinate Systems (SPCS) form the baseline for most localmapping activities. As such, the ALPs for all U.S. airports should bemonumented with reference points to provide for accurate coordinateconversion between World Geodetic Survey of 1984 (WGS 84)Latitude—Longitude, Earth Centered Earth Fixed (ECEF) X, Y, Z and localSPCSs or Universal Transverse Mercator (UTM). GPS and conventionalsurvey techniques are recommended for such monumentation.

[0841] The surveyed accuracy of the multi-use airport map is recommendedto be better than 0.5 meters for the horizontal and 0.1 meter forelevation. Of particular interest are the Airport Runway Touch DownMarker Reference Points (the precise coordinates of the center of arunway's touch down marker) and the Airport Runway Reference Points (theprecise coordinates along the centerline path of the runway). Inaddition, the precise locations of all turn outs and turn ins should beidentified in the airport map database.

[0842] Earth reference systems used in these locations should be ECEFX,Y,Z, North American Datum of 1983 (NAD 83) or WGS 84 latitude,longitude, MSL. These three models are compatible with GPS-basednavigation. Should the positions not be in one of these coordinatereference systems, then local airport multi-coordinate referencemonumentation should be used to support the required coordinateconversions.

[0843] Airport map latitude, longitude projections should be based uponthe Transverse Mercator, Lambert Conformal Conic, or Hotine ObliqueMercator These projections are used in state plane coordinate systems.Additional information on reference systems and projections is availablein North American Datum of 1983 (NAD 83), by Charles R. Schwartz.

[0844] The Manchester, N.H. (NH) airport map used in numerous testactivities was initially in NH State Plane Coordinate System feet. Thiscoordinate system was chosen for compatibility with existing maps andbecause it represented distances in linear feet rather than in degreesof latitude and longitude. The map was later converted to NH state planemeters and ECEF X,Y,Z representations. Manchester Airport was carefullysurveyed and monumentation was performed at multiple sites around theairport. The monumented points were referenced to the ECEF CartesianCoordinate System, NAD 83 Latitude, Longitude and Mean Sea Level (MSL),and the NH State Plane. Coordinate conversions were performed using themonumented points shown below. MULTI-REFERENCE MONUMENTATION FLAGPOLERUNWAY 35 END MONUMENT SITE #1 MONUMENT SITE #2 NEW HAMPSHIRE STATEPLANE COORDINATES NH SPCS X = 1045137.57 FT E NH SPCS X = 1048524.02 FTE NH SPCS Y = 158006.05 FT N NH SPCS Y = 154481.07 FT N NH ALT = 225.04FT NH ALT = 215.73 FT NH ALT = 68.59 M NH ALT = 65.75 M NAD83 LAT, LON,MSL LAT83 = 42.933325800 N LAT83 = 42.923628275 N LON83 = 71.439298894 WLON83 = 71.426691202 W MSL = 225.04 FT MSL = 215.73 FT MSL ALT = 68.59 MMSL ALT = 65.75 M ECEF X, Y, Z COORDINATES ECEF X = 1488741.9 M ECEF X =1489950.5 M ECEF Y = − 4433764.7 M ECEF Y = − 4434130.5 M ECEF Z =4322109.2 M ECEF Z = 4321318.4 M GEOID HT = − 28.24 M GEOID HT = − 28.24M WGS ALT = 40.35 M WGS ALT = 37.51 M

North American Datum of 1983

[0845] NAD 83 is a reference datum for the earth replacing the NorthAmerican Datum of 1927 (NAD 27). It was developed over many yearsthrough international efforts of many people. It was the largest singleproject ever undertaken by the National Geodetic Survey (NGS), spanning12 years.

[0846] The task involved 1,785,772 survey observations at 266,436 sitesin North and Central America, Greenland and the Caribbean Islands. Theobservations were made with all types of survey and measurementequipment from satellites to tape measures. The ultimate task was todevelop an earth model which satisfied a set of 1,785,722 simultaneousequations. The task was performed using a least squares approach andHelmert blocking. The purpose was to update NAD 27, calculate geoidheights at 193,241 control points and the deflections of vertical at thecontrol points.

[0847] The NAD 83 reference uses the Geodetic Reference System of 1980(GRS 80) ellipsoid based on the Naval Surface Warfare Center 9Z-2 (NSWC9Z-2) doppler measurements. The ellipsoid is positioned to be geocentricand have cartesian coordinate orientation consistent with the definitionof Bureau International de l'Heure (BIH) Terrestrial System of 1984.

[0848] NAD 83 data sheets contain information to update North American1927 references. The data sheets contain new information which isrelevant for precise surveys and users of GPS equipment. These include:precise latitude and longitude [DDD MM SS.sssss], latitude—longitudeshift in seconds of degree from NAD 27 to NAD 83, elevation above thegeoid with standard error, geoid height and standard error, state planeand Universal Transverse Mercator (UTM) coordinates.

[0849] These fundamental corrections and ellipsoid constants are thebasic parameters used in many coordinate conversions and navigationalprograms and form the basis of modem survey measurements.

[0850] GRS 80 used by NAD 83 has the following fundamental parameters:NAD 83 PARAMETERS PARAMETER VALUE UNITS Semimajor axis* 6378137 MAngular velocity* 7292115 × 10⁻¹¹ RAD/SEC Gravitational constant*3986005 × 10⁸ M³/SEC² Dynamic form factor 108263 × 10⁻⁸ unnormalizedSemiminor axis* 6356752.314 M Eccentricity squared 0.00669438002290Flattening 0.00335281068118 Polar Radius of Curvature* 6399593.625 M

World Geodetic Survey of 1984

[0851] WGS 84 was developed by the U.S. Department of Defense. Thereference system started with the same initial BIH conventions as NAD 83but, over the development, some parameters changed slightly. Thegeocentric ECEF system is based on a cartesian coordinate system withits origin at the center of mass of the earth. The system defines the Xand Y axis to be in the plane of the equator with the X axis anchored0.554 arc seconds east of 0 longitude meridian and the Y axis rotated 90degrees east of the X axis. The Z axis extends through the axis ofrotation of the earth. The WGS 84 reference uses the GRS 80 ellipsoid asdoes NAD 83. WGS 84 includes slight changes to GRS 80 parameters whichare identified below:

WGS 84 Parameters

[0852] WGS 84 PARAMETERS PARAMETER VALUE UNITS Semimajor axis* 6378137 MAngular velocity* 7292115 × 10⁻ ¹¹ RAD/SEC Gravitational constant*3986005 × 10⁸ M³/SEC² Dynamic form factor normalized −484.16685 × 10⁻⁶Semiminor axis* 6356752.314 M Eccentricity squared 0.00669437999013Flattening 0.00335281066474 Polar Radius of Curvature* 6399593.625 M

Comparison of NAD 83 and WGS 84

[0853] The North American Datum of 1983 (NAD 83) and World GeodeticSurvey of 1984 (WGS 84) attempt to describe the surface of the earthfrom two different perspectives. NM) 83 describes the surface of NorthAmerica using the Geodetic Reference System of 1980 (GRS 80) ellipsoidand over 1.7 million actual measurements. A least squares Helmertblocking analysis was performed by National Geodetic Survey (NGS) onthese measurements to determine the best fit solution to the actualmeasurements. NM) 83 uses monumented reference points across the countryto precisely reference various coordinate systems such as the StatePlane Coordinate Systems. WGS 84 incorporates positional referencesusing GPS and local references. Position determination by GPSincorporates precise Keplerian orbital mechanics and radio positioningtechnology. Clearly, the two systems are describing the same thing, butthe methods of determining a position are different.

[0854] Both NAD 83 and WGS 84 are based on BIF conventions. Though bothare based on the GRS 80 ellipsoid, small changes have occurred betweenthe two systems during their development. The basic difference in thedynamic form factor was attributed to GRS 80 using the unnormalized formwhile WGS 84 used a normalized form and rounded to eight significantfigures. Since other parameters derived from the dynamic form factordifferences usually appear after the eighth decimal place, most expertsfeel that the computational differences are of no significance.

[0855] Computations to determine the latitude and longitude from ECEFX,Y,Z coordinates highlight the small difference in the two referencesystems. It has been shown that the maximum error between the tworeference systems occurs at a latitude of 45 degrees. (Refer to NorthAmerican Datum of 1983, Charles R. Schwartz) No error occurs between thetwo systems in the determination of longitude. The maximum error amountsto 0.000003 seconds of arc which amounts to a latitude shift of 0.0001meters. For all practical purposes, the computational differencesbetween the two systems are negligible. This is an important point for,if the two earth models differed in basic latitude and kogitudecomputations, serious charting and navigational problems would occur andGPS navigation based on NAD 83 referenced maps would be seriouslylimited.

[0856] Both WGS 84 and NAD 83 have many common points used as localreference points. The differences between the two systems may reachseveral meters in rare locations, but on the average the systems shouldbe identical. Generally, measurement errors and equipment inaccuraciesintroduce more error than the differences in the two systems.

[0857] For airport mapping and GPS navigation we can assume that errorsdue to the differences between the NAD 83 and WGS 84 ellipsoid modelsare negligible. This implies that either system can be used incalculating navigational entities and performing precise mapping withGPS navigation. The monumented New Hampshire points established on NAD83 near the airport are well within the measurement accuracy of the GPSsurvey and navigation equipment. The documented offsets between NAD 83and WGS 84 for New Hampshire are 0.0 meters in the Y direction and −0.5meters in the X direction.

[0858] PHOTOGRAMMETRY

[0859] Photogrammetry techniques incorporating ground reference point(s)are recommended for creating electronic ALP's. Various techniques may beemployed to generate digital ALP's including aerial photogrammetry andground based moving platforms with integrated video cameras and sensors.The collected image data may be post processed to produce a highlyaccurate 2 or 3-D digital map of the surrounding area.

[0860] A digital map of Manchester (NH) Airport was created to supportearly test activities. The digital map was based on aerialphotogrammetry and GPS ground control using postprocessing software. AWild Heerbrugg aerial camera equipped with forward motion compensationwas used to capture the photogrammetry. The 3-D digitalization wasperformed using a Zeiss stereoscopic digitizing table. During thedigitalization process, numerous object oriented map layers wereconstructed to segregate various types of map information. The resulting3-D digital map had a relative horizontal accuracy of better than 1.0meter and a relative vertical accuracy of better than 0.1 meter acrossthe airport.

[0861] 3-D GRAPHICS FORMATS

[0862] Many digital map formats are in widespread use today. Translatorsare available to convert from one computer format to another. Maps maybe in either raster format (such as those generated by image scanning)or vector format (those developed on CAD and digitizing equipment). Thevector format provides a much more robust environment for developers ofATC and map display systems. Vector based drawings are represented byindividual vectors which can be controlled and modified individually orcollectively. This enables the developer to manage these entities at ahigh level rather than at the individual pixel level. The vectors mayrepresent specific geographical features (entities) in the map which maybe assigned to a particular map layer in a particular user definedcolor.

[0863] Since the map and ATC situation display are in a vector format, aconvenient method of graphically identifying and manipulatinginformation is available. The selection of a graphical symbol on thescreen through the use of a pointing device can be used to access anentity-related database or initiate an entity-based processing function.With raster-based images, there is no simple way to segregate thevarious pieces of map or graphic information for high level management.

[0864] Raster formats represent a series of individual pixels, eachpixel controlled as a function of a series of control bits. Typically aseries of three (3) words are used to describe the Red, Green and Blue(RGB) intensity of each pixel. Each pixel of information represents thesmallest piece of the image and has no information about the largergraphical entity that it is part of. From a management perspective, thisintroduces additional complications for even the simplest graphicalmanipulation tasks such as suppressing the display of a series of rasterbased topographical contour lines in the airport map.

[0865] A high level management capability is required for ALP graphicentity control. The current raster-based maps do not provide thisfunctionality, hence additional processing is required each time the mapis displayed or modified. For raster-based maps to provide thiscapability, the pixel elements must be functionally organized in somemanner to support the higher level management functions described inthis application. For this reason, raster scan map formats are notrecommended for ALPs at this time.

[0866] Vector formats may be in ASCII or binary and may be constructedusing different rules for their generation. The example below uses theAutoCADTM DXF standard drawing format. (AutoCAD is a registeredtrademark of AUTODESK, Inc.) AutoCADTM is one of the most popularComputer Aided Design (CAD) software packages in the world today and istypical of vector ALP formats. The DXF map format may be easilyconverted to almost any CAD drawing format. AUTOCADTM DXF ALP FORMAT NEWHAMPSHIRE STATE PLANE ECEF X, Y, Z FEET METERS 3DFACE 3DFACE 8 8BUILDING BUILDING 10 10 1046289.75 1489279.59 20 20 154935.219−4434265.78 30 30 256.499 4321428.53 11 11 1046289.75 1489277.26 21 21154935.219 −4434258.83 31 31 223.7 4321421.72 12 12 1046245.3751489258.04 22 22 155032.25 −4434243.98 32 32 223.7 4321443.43 13 131046245.375 1489260.37 23 23 155032.25 −4434250.92 33 33 256.4994321450.24 0 0

[0867] The two formats shown above represent the vertical side of abuilding which is, by AutoCADTM convention, a 3-D face. Since the twocoordinate systems are different, one must appropriately set therespective viewpoint for each display. This is accomplished in theinitial ALP DXF configuration declarations. In a similar fashion, thedrawing could be converted to other coordinate systems such as UniversalTransverse Mercator (UTM) using a DXF coordinate conversion utilityprogram such as TRALAINE™ (available from Mentor Software, Thornton,Colo.

[0868] The above example represents just one of the thousands ofentities making up an ALP. Many commercial graphical libraries andcommercial CAD software products are available today for theconstruction and use of ALPs and other 3-D graphic entities.

[0869] The use of modern digital Computer Aided Design (CAD) techniquesis required for the development of electronic map databases. The use ofGPS-based, ground referenced photogrammetry with post processing 2 or3-D digitalization provides a cost effective, highly accurate andautomated method of constructing the 2 or 3-D ALP.

[0870] An industry or international standard format for the constructionand interchange of digital graphical information should be used.Numerous standards are established with readily available softwaretranslators for conversions between the various formats. Map fileformats may be binary or ASCII characters.

3-D Object Oriented Map Layers

[0871] When stored in a digital format, the ALP should be arranged inobject oriented map layers. Proper layering of information provides thecapability to present only the information that is needed for aparticular purpose. For example, navigational maps should notnecessarily include all the digital layers of the ALP. A simplifiedversion of the map showing only runways, taxiways, navigationalreferences (landmarks) and gate areas should be used. The use ofspecific layers of interest provides the following advantages:

[0872] minimizes possible confusion in presenting too much informationto the pilot or controller

[0873] decreases reaction times of controller and pilot by onlypresenting what is needed

[0874] reduces computer memory requirements

[0875] minimizes computer processing requirements

[0876] provides faster display updates (fewer pixels to redraw)

3-D Digital Map Coordinate Systems

[0877] In order to integrate GPS navigational data with 2 or 3-D maps,the potential map formats must be evaluated for compatibility and easeof use with the navigational output and coordinate reference system. Thetable below lists twelve of the most likely combinations. COMBINATIONSOF MAPS, NAVIGATIONAL PARAMETERS AND MATHEMATICAL COORDINATE REFERENCESMATHE- MATICAL NAVI- DIGITAL GATIONAL COORDINATE # MAP FORMAT I/O FORMATREFERENCE 1. LAT, LON, LAT, LON, LAT, LON, MSL MSL MSL  2.* LAT, LON,LAT, LON, ECEF MSL MSL 3. LAT, LON, STATE ECEF MSL PLANE/UTM 4. LAT,LON, ECEF ECEF MSL 5. STATE STATE STATE PLANE/UTM PLANE/UTM PLANE/UTM 6.STATE LAT, LON, LAT, LON, PLANE/UTM MSL MSL  7.* STATE LAT, LON, ECEFPLANE/UTM MSL 8. STATE ECEF ECEF PLANE/UTM 9. ECEF ECEF ECEF 10.* ECEFLAT, LON, ECEF MSL 11.  ECEF LAT, LON, LAT, LON, MSL MSL 12.  ECEF STATESTATE PLANE/UTM PLANE/UTM

[0878] Other permutations are possible for the different combinations ofcoordinate systems, map references and navigational output formats.Other combinations can be “made to work”, but based on arithmeticprecision, map availability and software complexity, the combinationsidentified with an asterisk satisfy the evaluation criteria mosteffectively.

[0879] The table below presents a compliancy matrix, where each of thetwelve combinations are evaluated against a set of criteria. Thecriteria used are described in greater detail following the table.COMPLIANCY MATRIX * * * MAPPING FORMAT: -1- -2- -3- -4- -5- -6- -7- -8--9- 10- 11- 12 EXISTING MAP DATA Y Y Y Y Y Y Y Y N N N N RECOGNIZABLEMAP Y Y Y Y Y Y Y Y N N N N CONV. SW EXISTS Y Y Y Y Y Y Y Y Y Y Y Y EASY3D - 2D CONV Y Y Y Y Y Y Y Y N N N N MULTI-USE FORMAT Y Y Y Y Y Y Y Y NN N N WORLD WIDE SYSTEM Y Y Y Y N N N N Y Y Y Y LINEAR SYSTEM N N N N YY Y Y Y Y Y Y GPS COMPATIBLE Y Y Y Y N N N N Y Y Y Y SEAMLESS SYSTEM N NN N N N N N Y Y Y Y NAV INPUT-OUTPUT: -1- -2- -3- -4- -5- -6- -7- -8--9- 10- 11- 12 RECOGNIZABLE Y Y N N N Y Y N N Y Y N ACCEPTED STANDARD YY N N N Y Y N N Y Y N WORLD WIDE USE Y Y N Y N Y Y Y Y Y Y N GPSCOMPATIBLE Y Y N Y N Y Y Y Y Y Y N CHARTS AVAILABLE Y Y N N Y Y Y N N YY Y COORD REFERENCE: -1- -2- -3- -4- -5- -6- -7- -8- -9- 10- 11- 12RECOGNIZABLE REF. Y N N N Y Y N N N N Y Y WORLD WIDE USE Y Y Y Y N Y Y YY Y Y N SIMPLE NAV. MATH. N Y Y Y Y N Y Y Y Y N Y NAD83 & WGS84 REF Y YY Y Y Y Y Y Y Y Y Y SINGLE 3D ORIGIN N Y Y Y N N Y Y Y Y N N LINEARSYSTEM N Y Y Y Y N Y Y Y Y N Y UNITS OF DISTANCE N Y Y Y Y N Y Y Y Y NY * * * TOTAL YES COUNT: -1- -2- -3- -4- -5- -6- -7- -8- -9- 10- 11 1215 18 13 15 12 14 17 14 13 16 13 11

[0880] CRITERIA DEFINITIONS MAPPING: COMPATIBILITY WITH Existing digitalmap data EXISTING MAP DATA is available for the airport and surroundingarea. RECOGNIZABLE MAP A map which is instantly recognizable, one whichresembles the surface on which we live. The map should not need to bedifferentially corrected from the reference geoid. CONVERSION SW EXISTSCommercially available software exists to convert from one 3-D mapreference system to the other EASY 3D - 2D Digital map presentationsCONVERSION can be easily converted from 3-D to 2-D by setting thealtitude to zero without any additional mathematical conversions in theraw map data or in the 3-D graphical interface. MULTI-USE FORMAT The mapdata is in a standard format which can satisfy multi-use needs such asMaster Plans, construction needs, ATC and general navigation. WORLD WIDESYSTEM References in the map are with respect to world wide datums andaccepted world wide mapping units. LINEAR SYSTEM The axes and units ofthe map are linear and represent distance. GPS COMPATIBLE Mapping unitsand presenta- tions are directly compatible with existing GPS receiveroutput formats and calculation references. SEAMLESS SYSTEM Maps do nothave mathematical/ physical discontinuity, the map format must beseamless on a world wide basis. For example UTM maps do not cover polarregions and map edges do not match on 6 degree boundaries when placedtogether. NAVIGATIONAL OUTPUT: RECOGNIZABLE The final navigationaloutput should be instantly recognizable; i.e. if LAT, LON, MSL output isused, one can instantly visualize a location on the earth, while if ECEFoutputs are given it is difficult to visually picture a point in space.ACCEPTED STANDARD Navigational format is an accepted standard; i.e. LAT,LON, MSL WORLD WIDE USE The navigational format is usable over theentire world. GPS COMPATIBLE Navigational format is compatible withexisting GPS receiver outputs. CHARTS AVAILABLE Paper and digital chartsare available. COORDINATE REFERENCE: WORLD WIDE USE The coordinatereference system is recognized throughout the world. SIMPLE NAVIGATIONThe coordinate system lends MATHEMATICS itself to simple linearnavigational mathematics. NAD83 AND WGS84 REF. The reference system iscompatible with North American Datum of 1983 and World Geodetic Surveyof 1984. SINGLE ORIGIN The system has one and only one origin. LINEARSYSTEM The system is a linear coordinate system. UNITS OF DISTANCE Thecoordinate system is based on units of distance rather than angle.

[0881] To illustrate the differences between GPS trajectories displayedin maps using different coordinate systems, the following plot examplesare provided. FIG. 12 shows a plan view of latitude versus longitude.FIG. 14 shows the same trajectory in ECEF X and Y coordinates. FIG. 13depicts the MSL Altitude versus Time while FIG. 15 shows the ECEF Xvalues versus Time. Note the distortion between the latitude, longitude,MSL altitude and the ECEF X,Y, and Z coordinates. (The small rectangleson each plot represent waypoints along the trajectory path.)

[0882] Plotting points in the map database requires that thenavigational computations provide output which is compatible with themap database coordinates. Combination #7 in the previous Table includesa map database which is in a State Plane Coordinate System and anavigational output in latitude, longitude and MSL. Additionalconversions are required to convert the navigational data to state planecoordinates prior to plotting the points in the map database. A moreconvenient map, navigational and coordinate reference frame is required.

ALP Summary and Recommendations

[0883] Future airport maps or modifications to existing maps should makeevery attempt to utilize recent technological advances in theirconstruction. The following items are guidelines for future mapdevelopment:

[0884] Precise, 3-D airport maps (ALPs) should be created and maintainedfor all major and reliever airports.

[0885] ALPs should be constructed to satisfy multiple user requirements.

[0886] Electronic graphical design tools should be used in ALPconstruction. Computer Aided Design tools should be used whereverpossible.

[0887] Standard graphical formats (either ASCII character or industrystandard binary file formats) should be used.

[0888] The concept of electronic layers should be used to identify andisolate entities in the map database.

[0889] Airport Reference Points (ARPs) should be located at preciselymonumented positions around the airport. ARPs should be referenced tothe coordinate systems of interest (such as LAT,LON,MSL, ECEF X,Y,Z andthe SPCS).

[0890] At least three (3) ARPs, located within the airport confines inareas which are not likely to be disturbed, are recommended. Wherepossible, these points should be placed in the far comers of the airportto form a triangle. These points should be surveyed with GPS basedsurvey equipment and monumented physically on the ground and within thedigital map database.

[0891] ARPs should be recomputed as necessary to assure accuracy of thenavigation and ATC functions. Re-monumentation may be required as a partof airport construction and expansion. Natural phenomena such as platetectonics, may force re-monumentation of the airport. When ARP positionschange more than 0.5 meters horizontally and 0.1 meters vertically,re-monumentation is recommended.

[0892] Areas used by aircraft such as runways, taxiways, gate areas andramps should be surveyed to a horizontal accuracy of 0.5 metershorizontally and elevation to 0.1 meters.

[0893] The use of photogrammetry is suggested as an efficient means ofcreating a digital database of an existing airport.

[0894] Earth reference systems used for the various map projectionsshould be the NAD 83 or WGS 84. Older, previously accepted datums whichdo not correlate with GPS navigation or surveys should be avoided.

[0895] ALPs should be compatible with cockpit instrumentation and ATCdatabases.

[0896] GPS calibration areas should be located at all gates or areaswhere aircraft remain stationary. These areas should be identified inthe airport digital map. The purpose of the calibration area is to allowthe pilot to check the accuracy of the on board GPS equipment.

[0897] Cost effective and highly accurate mapping technology isavailable to allow for the generation of multi-use maps which should becompatible with a host of platforms and potential uses. The exploitationof these common use maps will enhance master planning, aviation and AirTraffic Control (ATC) capabilities. Maps developed to national standardswill provide a cost effective navigational and ATC data base.

[0898] SUMMARY, RAMIFICATION AND SCOPE

[0899] The presented invention provides a valuable enhancement to thecurrent airport environment. This enhancement will result in safer airtravel and more efficient operation of our currently capacity limitedairports. Human blunders in the cockpit and in the control tower havecost hundred of lives in the past. Seamless airport operations willresult in lower air traffic controller and pilot workloads through theuse of automation processing. Advanced situational awareness displaysshowing travel paths, and clearance compatible mirrored navigationautomation processing will reduce the likelihood of human blunders inthe control tower and in the cockpit resulting in a safer airportenvironment. The elimination of out dated single function navigation andsurveillance systems will result in significant cost savings for theairport authority and the FAA. The cost effective nature of this GNSSbased airport control and management system will allow deployment atsmaller airports resulting in safer operations and better on timeperformance throughout the whole aviation system.

[0900] It is obvious that minor changes may be made in the form andconstruction of the invention without departing from the material spiritthereof. It is not, however, desired to confine the invention to theexact form herein shown and described, but is desired to include allsuch a properly come within the scope claimed.

1. A GNSS compatible airport control and management method providing acomputer human interface for use by a controller in the monitoring,control and management of at least one vehicle selected from the groupcomprising aircraft and ground vehicles the system comprising the stepsof: (a) displaying on at least one display device interfaced to anairport control and management processor with data entry capabilitymeans at least one airport control and management command of a pluralityof commands selected from the group consisting of Display View, ArrivalWaypoints, Departure Waypoints, Vehicle Data and Airport Lights; (b)determining in said airport control and management processor theascertained position of said at least one vehicle, said position beingGNSS referenced; (c) using said data entry capability means to allow acontroller to select said at least one airport control and managementcommand and (d) using said display means to present on said at least onedisplay device said at least one vehicle's ascertained position to thecontroller, thus allowing the controller to monitor the position of saidat least one vehicle.
 2. A GNSS compatible airport control andmanagement method according to claim 1, wherein said ascertainedposition is derived from a surveillance system selected from the groupcomprising automatic dependent surveillance, radar surveillance and ModeS surveillance.
 3. A GNSS compatible airport control and managementmethod as recited in claim 2, wherein said ascertained position isderived from Mode S multi-lateration.
 4. A GNSS compatible airportcontrol and management method as recited in claim 2, further comprising:(a) using said display means to present said display view command onsaid at least one display device; (b) using said data entry capabilitymeans to allow a controller to select said display view command,resulting in the presentation of a list of graphic views on said atleast one display device; (c) using said data entry capability means toallow a controller to select a particular graphic view from said list ofgraphic views resulting in said display means presenting said selectedgraphic view on said at least one display device.